Abstract: Abstract: The accelerations of boom sprayer caused by soil unevenness may lead to the spray boom's elastic deformation, which would cause uneven spray deposit. In order to attenuate spray boom's elastic deformation, a finite element model was built based on ANSYS, and then the modal information of the model was obtained by numerical modal analysis. For the simplification of spray boom's finite element model, modal test was used to validate the finite element model and its modal information, the test introduced a way that multi points and multi directions exciting, one point and one direction response to obtain the frequency response functions (FRFs). Exciting signal was generated by a hammer (LC-1) and detected by a force sensor (AD-YD305). Response signal was measured by an acceleration sensor (YD-1). After the exciting and response signals were measured, the FRFs were obtained in SD380 dynamic signal analyzer through fast frourier transform (FFT), and the modal parameters were identified in STAR7. After the test, a comparison was conducted between test and calculation. The result showed that the first 6 modes' resonance frequency difference between finite element model and test modal model were less than 10%, the modal assurance criterion (MAC) between finite element model and test modal model of the first 6 modes were more than 0.8, which indicated that the finite element model and the modal information that the model contained could be used for engineering research. Modal analysis result showed that the first mode frequency of spray boom was 9.16 Hz, while the excitation frequency of spray machine chassis was 0-10 Hz. It was apparent that the first mode frequency of spray boom was between the range of the excitation frequency of spray machine chassis. Since the spray boom was fixed on the chassis's frame, the motions of chassis caused by uneven ground would directly transfer to the spray boom, which may lead to spray boom's elastic deformation. In order to study the elastic deformation of spray boom under different boom motions based on finite element model, the elastic deformation of spray boom's end caused by ----was analyzed using harmonic response method by a frame spray boom model established based on ADAMS. All excitation frequencies were between 0-10 Hz, and amplitudes of jolting, yawing and rolling were 50 mm, 5°, and 5°, respectively. These motions led to the maximal elastic deformation at the end of spray boom on the corresponding plane of about 80, 10, and 10 mm, respectively. The harmonic response analysis showed jolting was the main factor affecting elastic deformation if spray boom, and thus the spray boom's elastic deformation caused by jolting should be reduced primarily. In order to reduce the elastic deformation of spray boom, two symmetrical cables that were defined as elastic bodies were added to the frame spray boom model. An included angle between cable's projection on XOY plane and spray boom length (z direction) was designed to ensure that the cables could effectively reduce spray boom's elastic deformation. Two ends of cable were connected to frame and spray boom respectively through a spherical joint. Obviously, installation position of cables may impact the effect of reducing spray boom's elastic deformation. In order to further investigate the variation of elastic deformation associated with different installation position of cables, 4 different installation positions were selected along reinforce steel pipes of the spray boom according to the structure of spray boom including the position that was 1/4, 2/4, and 3/4 away from the middle point of spray boom and the end of the spray boom. The elastic deformation of spray boom was determined with an excitation frequency between 0-10 Hz when the cables were installed at the 4 different positions. The results showed that the installation position at 3/4 away from the middle point of the spray boom was optimal and the other positions were not good for reducing elastic deformation of spray boom since the elastic deformation of spray boom was minimal with less than 10 mm among the four different treatments, which was lower than that (80 mm) when no cable was installed.