Pig dung and wheat straw (the ratio of pig dung to wheat straw was 1∶1, 2∶1, 3∶1)were used as fermentation materials. The experiments were carried out at 35℃. The biogas production rate, cumulative biogas yield, methane content, material reduction, pH value and NH3-N content were tested. The results showed that the co-digestion of pig dung to wheat straw could increase the biogas yield and material reduction of wheat straw. The biogas production yield of 1∶1 was highest (383.0mL/g), which was 1.6 times of biogas production yield of wheat straw (231.8mL/g). VS reductions of combination materials were 12.0%～26.9% higher than wheat straw. Compared with wheat straw, the NH3-N contents of combination materials increased by 35.6%～64.8%. Reasonable co-digestion ratio of livestock dung and crop straw could increase the biogas production rate and utilization of crop straw.