Abstract: In order to solve the problem of straw pretreatment in biogas engineering, this study proposed a physical-chemical combination pretreatment of the straw based on twin-screw extruder for biogas production. Taking rice straw as the material, the experiments were divided into twin-screw physical-chemical combination pretreatment group, unique twin-screw physical pretreatment group, unique chemical pretreatment group and no pretreatment group, and the feeding amount above was 20 g by dry weight. The results of the experiments showed that: (1) the cumulative biogas yield of the four groups were 2 340.5, 1 750, 2 025.5 and 1 868.5 mL respectively; (2) the results of analysis of variance (p<0.05) on the biogas yield per gram of total solid (TS) were that: for chemical method p=0.0158, for physical method p=0.4828, for physical-chemical interaction method p=0.0422; this showed the physical-chemical combination pretreatment was significance to biogas yield; (3) after twin-screw pretreatment, the length of the material was 5-10 mm and the width was 1-2 mm. The results showed that the physical-chemical pretreatment with twin-screw extruder is one of the potential pretreatment, and the transformation in the form of the straw can meet the need of accessing and discharge for CSTR and change the flow field in the CSTR when stirring.