Abstract: Fine and large scale CFD simulation of the whole reactor core is an important methodology in the research and design of HPR1000 and digital reactor. Based on a series of reasonable simplification of the core, the geometry model of the whole core were built for HPR1000. Meanwhile, the fuel assembly is discretized in group and the CFD model of the whole core is obtained. Besides, the distribution of flow field and the parameters of thermal hydraulics are obtained by the fine and large scale CFD simulation for the whole core. The results verify the rationality of design parameters of reactor core of HPR1000 and provide reference to the optimal design and safe operation of reactor. The results show that: due to the combined action of the 1/4 symmetrical structure of the HPR1000 reactor core  and the 1/3 symmetrical structure of the coolant inlet and outlet of "three in and three out", the flow distribution factor of the core first increases and then decreases in the radial direction, and the maximum flow is not in the center of the core; the maximum temperature of the fuel assembly on the cross section of the inlet nozzle is about 331.2℃, and the temperature distribution is asymmetrical. The maximum temperature region is not in the center of the core, which is similar to the trend of the core flow distribution factor. It is the result of the joint action of the core power distribution and the coolant flow distribution.