Abstract: Under mesothermal temperature, the effects of pig manure addition on two phase anaerobic digestion were investigated with different volume ratio of straw and pig manure (1:0, 5:1, and 1:1). After digestion, the materials in top, medium and bottom of CTP were taken out to determine the biogas potentials. The results demonstrated that the biogas production was elevated from 314 L to 500 L, while the stabilities of pH value, acid production were reduced. The volume addition of 20% could promote digestion performance. The biogas potential tests showed that the biogas production in medium of CTP was minimum, while it was maximum in the bottom. This indicated that acidogenic process was prominent in the medium, while methanogenic process was dominant in the bottom of CTP. The volume addition of 20% manure could promote the distribution of acidogenesis and methanogenesis, and strengthen the CTP advantages.