Related research at home and abroad have shown coaxial contra-rotary drilling can effectively reduce drilling tool vibration and improve the rock breaking efficiency. There are few researches on the improvement level of drilling efficiency of coaxial contra-rotary drilling compared with traditional drilling. In view of the above， the finite element model of interaction between coaxial contra-rotary bit and rock is established and the finite element model of interaction between conventional bit and rock is established. The rock breaking efficiency of the two kinds of drill bits is compared quantitatively with rock breaking specific work as evaluation index. The orthogonal experiment is designed by defining five core parameters， the size difference between the inner and outer wall of the coaxial contra-rotary bit， the gap between the inner and outer wall of the coaxial contra-rotary bit， the ratio of the inner and outer wall thickness to the size difference between the inner and outer wall of the coaxial contra-rotary bit， the rotating ratio of the inner bit and outter bit and the bottom height difference of the inner and outer bit. The simulation analysis is completed according to the orthogonal experiment. The result show that the height difference between the internal and external bit and the internal and external bit clearance have little influence on the rock breaking specific work， while the size difference between the inner and outter bit， the rotating ratio of the inner and outter bit and the ratio of the wall thickness of the inner bit to the size difference between the inner and outer wall of the coaxial contra-rotary bit have significant influence on the rock breaking specific work.