Abstract: Abstract: A kneading pretreatment was proposed to reduce the connection force between the shell and meat in a typical fresh shrimp (Penaeus vannamei). The influencing factors were optimized using measured parameters to improve the efficiency of shrimp shelling and the quality of meat. Fresh Penaeus vannaeus were taken as the research object in the experiment with the body length of (12.1±0.5) cm, the first segment thickness of (10.9±0.9) mm, the total weight of (10.6±1.5) g, the lateral wedge angle of 4.8°±1°, as well as the ventral and dorsal wedge angle of 5.9°±0.6°. Prior to the experiment, the key factors were determined to influence the shrimps kneading, including the normal pressure, the total kneading distance, and kneading direction (inverse proportion of direction). A belt-type kneading device was designed according to the needs of experiments and the body characteristics of shrimps. The upper and lower kneading belt in the device were in relative motion to achieve the kneading of the middle shrimp. The dip angle of two kneading belts was set at 5.4°, in order to make the kneading belt better fit the shrimp body. Specifically, the distance between two kneading belts was utilized to control the amount of normal pressure of shrimps kneading, whereas, the relative rotation distance was to adjust the total kneading distance. The relative direction of kneading belt movement was used to tailor the inverse proportion of direction. Before the rolling test, fresh shrimps were treated at 1℃ for 15min, further to simulate the environment of shrimp in the modern processing section (washing and grading in a mixture of ice and water). Just then, fresh shrimps had already passed out in such an environment, which was also helpful for the later rubbing work. The influencing factors were set as the normal kneading pressure, the total kneading distance, and direction, whereas, the evaluation indexes were the stripping index, juice loss rate, and breakage rate. Box Behnken design (BBD) in the Design-Expert8.06 software was selected to first conduct a single-factor experiment, and then a multi-factor one. A regression equation was also established using a Response Surface Method (RSM). A combination of optimal parameters was obtained: 11.8 N of kneading normal pressure, 70 cm of total kneading distance, inverse proportion of direction 30%, while the stripping index of 1.41, juice loss rate of 3.44%, and breakage rate of 4.9%. The experiment was carried out again under the optimal parameter condition, where the error between predicted and true value was less than 5%, indicating a reliable performance. The stripping index was the average of shucking grades for each shrimp in the group, whereas, the inverse proportion of direction was the percentage of the total distance kneaded in the opposite direction. The force of shrimp was calculated according to the three-layer shell, epithelium and muscle of shrimp during kneading. A specific mechanism was proposed for the shell loosening of shrimps, combined with the force and experimental observation of kneading. The first was the deformation of the shrimp body caused by extrusion pressure; the second was the tearing effect of shearing force on the shell; the third was the rolling to transmit both deformation and tearing of shell into the whole circumference of the shrimp body. The structures of kneaded and unrubbed shrimp were compared under a scanning electron microscope (SEM). It was found that the separation between the shell and muscle of kneading shrimps was significantly higher than that of unrubbed ones, indicating that the kneading significantly promoted the separation. There was an obvious shell/meat separation, such as fold fractures in rolling, but no separation of epithelium from shrimp for less loss of juice. Consequently, the kneading can keep the fresh characteristics of shrimps with a nice taste for a longer shelf life. There were also no additives and high-energy consumption for both environmental protection and energy-saving during fresh shrimps processing.