Abstract: The neutron time-space kinetics for accelerator driven sub-critical system (ADS) was simulated by using improved quasi-static approximation combined with Monte Carlo neutron transport program (IQS/MC) method. The physical model of accelerator driven system of target and reactor coupled reference scheme was regarded as an example, the dynamics in two conditions of inserting beam and lifting fuel assembly were simulated, and the core total relative power and three-dimensional gird distributions of relative neutron fluence rate of energy group separated and relative power along with time were obtained. The calculation results of IQS/MC method and point reactor method were compared and analyzed, the simulation results conform to physical laws, and the comparative result of two methods is consistent with the foreign reference. The results show that IQS/MC method is suitable for transient security analysis of neutron time-space kinetics for ADS sub-critical reactor.