This paper studied the co-pyrolysis behavior of crop straw and swill-cooked dirty oil (≈ 2:1 ratio by weight) at 10, 30, 50K/min, in dynamic thermal gravimetric analyzer (TGA) under inert atmosphere, from 303K to 973K. The kinetic parameters were calculated using the method of Ozawa-Flynn-Wall, and mechanism was hypothesized as first-order model. The results showed that the dirty oil led degradation temperatures to slide towards higher slightly, meanwhile broadened the temperature interval of decomposition. However, the presence of dirty oil had little impact on activation energy. These findings indicated a significant synergistic relationship between straw and dirty oil, and it was practicable for co-pyrolysis from the viewpoint of thermal and kinetics analysis.