It is well known that for an associative ring R, if ab has g-Drazin inverse then ba has g-Drazin inverse. In this case, (ba)d = b((ab)d)2a. This formula is so-called Cline’s formula for g-Drazin inverse, which plays an elementary role in matrix and operator theory. In this paper, we generalize Cline’s formula to the wider case. In particular, as applications, we obtain new common spectral properties of bounded linear operators