Abstract: The simulation of the 3D-cylinder reactor core neutron space-time kinetics by improved quasi-static method was studied, and the computation program was developed. For the supposable modular high-temperature gas-cooled reactor model, the core neutron space-time kinetics was simulated. The calculated results obtained from this program and CITATION code are accord with each other at the initiatory state. The variance of the core reactivity, the average neutron fluence rate of each group, and the relative power along with time were computed for the dynamic simulation of the given model. The requirement of the real-time computation is satisfied under a certain precision.