Abstract: Abstract: Aiming at to solve the problem of inoculation failure caused by the cracks and the needle impact during the injection of chicken embryo vaccine, a mechanical model of impact during eggshell injection was established and analysied. First, the relationship between the resultant force per unit length of the injection hole and the initial injection velocity, the mass of the injection system and the cone angle of the needle was derived from the impulse theorem and the law of conservation of momentum. In order to verify the correctness of the mechanical model, and to further explore the relationship between eggshell deformation, stress and strain with taper angle, initial injection speed and mass of the injection system during the injection of chicken embryos, ANSYS software was used to simulate the impact of the needle on the eggshell. The simulation results verified the accuracy of the mechanical model, and it was preliminarily determined that the range of the initial injection velocity was 0.5-0.8 m/s, and the range of the injection system mass was 0.5-1.2 kg. The needle cone angles are 10°and 15°. Second, in order to complete the chicken embryo injection test, a chicken embryo injection and micro-crack detection device was established. The device consists of the high-speed camera, injection system, buffer mechanism and crack detection device of the injection hole of chicken embryo. The high-speed camera can measure the initial speed of injection, and the injection system can realize the injection of chicken embryo, even can change the mass of the injection system arbitrarily, and select different specifications the needle can change the cone angle, and the buffer mechanism can effectively avoid the crack of chicken embryo due to vibration. The crack detection device is mainly composed of CCD industrial camera, egg support and cold light source, which can ensure the accurate identification of chicken embryo crack and the smooth progress of injection parameter optimization test. Furthermore, an orthogonal experiment was designed to extract the characteristics of the injection hole cracks with image processing technology, and calculate the injection hole crack effective area index and the crack effective contour index, judgment whether the injection of cracked egg embryos and intact egg embryos. Eggshell was a micro porous structure, and the permeability of the eggshell was inconsistent. The eggshell need to be irradiated with a cold light source during the image processing, and the collected source image has bright spots. Eggshell bright spots cannot be effectively removed, and effective crack features cannot be retained using traditional threshold segmentation algorithm. Therefore, an eggshell bright spot elimination algorithm was used to retain the crack features of the chicken embryo injection hole and remove the bright spots to the maximum extent. Finally, a three-factor two-level interaction analysis of variance method was used to determine the optimal injection parameter combination: the initial injection velocity was 0.6 m/s, the needle cone angle was 10°, and the injection system mass was 1.0 kg. 7-14 day-old chicken embryos were used to test under the optimized parameters, the injection success rate was 98.75%.