The main reasons of low drilling efficiency in elastic-plastic compact mudstone are analyzed. On this basis, a new type bit with sharp-tooth PDC was developed. The optimal design in geometric structure of PDC, cutting structure and hydraulic structure makes a good performance of the bit. Compared with ordinary PDC bits, it provides longer service life and higher drilling efficiency (average in 300m and 3～4m/h respectively) in elastic-plastic compact mudstone drilling.