To study the relationship between shear band and brittle-ductile transition behavior of typical polymer bonded explosives（PBX） under the influence of temperature， the mechanical response of PBX at 323-363 K was tested by using DIC digital image technology， in-depth analysis of shear band evolution law and failure mode. At the same time， the brittle-ductile transition mechanism of PBX under temperature effect was analyzed based on the theoretical model of crack slip. And the critical conditions of wing crack development and plastic slip area were obtained by considering the effect of temperature. The results showed that at 323-363 K， the variation of the shear band width of the PBX depended on the competition mechanism of dilation and shrinkage. There are four main mechanisms： Ⅰ. Dilatation and shrinkage reach equilibrium； Ⅱ. Shrinkage is dominant； Ⅲ. Dilatation is the main controlling factor； Ⅳ. Dilatation dominates intermittently. Combined with the principle of Griffith energy release， it is found that the shear strength， cohesion and fracture toughness of the specimen are the key controlling factors of the brittle-ductile transition. Under the condition， the judging basis of PBX brittle-ductile transition was obtained. When the condition of wing crack instability was met， the macroscopic failure mode tends to split failure； and when the critical condition of the plastic slip area was achieved， the multiple slip zones are connected to each other to form a plastic slip surface， and the macroscopic failure mode was dominated by the ductile fracture of shear crack slip.