We propose a novel scheme of multi-rate quasisynchronous coherent time-spreading OCDMA system, employing orthogonal variable spreading factor (OVSF) codes with a zero-correlation zone. Within permissible time delay, the aperiodic cross-correlation of OVSF with a zero-correlation zone equals zero. Therefore, multipleaccess interference and beat noise can be removed in multirate quasi-synchronous coherent time-spreading OCDMA system, and the near-far problem can also be eliminated. Simulation of eight simultaneous users with 2.5 Gbit/s, 1.25 Gbit/s and 0.625 Gbit/s is demonstrated, where the fiber link consists of 20 km single-mode fiber, plus 2 km Dispersion Compensating Fiber. The results show that OVSF codes with a zero-correlation zone can be employed to multi-rate quasi-synchronous coherent time-spreading OCDMA system.