Abstract: Large pitch was used to speed up scanning in helical cone-beam CT, but its reconstruction remains a challenging problem. The Single-Slice ReBinning method (SSRB), proposed by Noo et al, can obtain high image quality at large pitch, but artifacts appear when pitch is too large for given detector. In this paper, a new approximate reconstruction scheme, i.e. Improved Single-Slice ReBinning method (ISSRB) is described. It modified the key rebinning step of SSRB. Theoretical considerations and reconstruction of simulation data are presented in comparison to SSRB in the paper. Results show that the pitch of proposed method is (1+tan²δ) times larger than that of SSRB for given detector size, and the reconstruction image quality is comparable or even better.