Abstract: Technology of high moisture textured soy protein(HM-TSP) wasdeveloped, by using a twin-screw extruder lab station with a long cold die.The effects of processing variables with material of defatted soy meal, such asscrew speed, meal moisture, feeding rate, and barrel temperature of extrusion process on the textural and color properties of soy protein were analyzed experimentally. The micro-structure of high moisture textured soy protein was analyzedusing scanning electric mirror. Results indicate that the extrudates have thebest texturizing degree, colors,and sensory characteristics when the barrel temperature is at about 150℃. With the increasing meal moisture, the texturizing degree, adhesiveness, and brightness index of the extrudates increase, but the hardness and chewiness decrease gradually. With the higher screw speed, the texturizing degree, hardness,adhesiveness, and chewiness are increased gradually. The sensory evaluation of extrudates is influenced observably by the feeding rate. When the feeding rate isat a higher level, the appearance of the extrudates is crude, and the texturizing characteristics are reduced. The feasible processing variables are: barrel temperature 145～155℃, meal moisture 45％～50％, screw speed 90～160 r/min, feeding rate 20～40 g/min. The microstructure of the extrudate was studied on three profiles by scanning electron microscopy (SME). According to processing testing and profile analysis of SME, the "membranous air cavity" hypothesis of extrusion texturization mechanism was discussed, and it could be guided to the production of high moisture textured soy protein.