In order to study the effects of extruding technological parameters on in vitro protein digestibility of flaxseed, extruding experiments were carried out by SLG67-18.5 type twin-screw extruder. The effects of temperature, moisture content, rotation speed of screw and feeding speed on in vitro protein digestibility of flaxseed were investigated respectively. The relations between in vitro protein digestibility and each parameter were obtained with normal orthogonal rotary regression method. Subsequently, the regression model of in vitro protein digestibility was established, and the microstructure of extruded flaxseed was also analyzed. According to the results, temperature and rotation speed of screw didn't have obvious influence on in vitro protein digestibility, but the interaction of them were obvious. The experimental results provided a useful formation to the industrial production of flaxseed extrusion. 