Abstract: For CAP1000 reactor, the coolant is injected in the reactor vessel under the accident condition through the method of direct injection. Because of the arrangement of the injection nozzle and the internals, the low temperature water has great effect on the reactor internals. The surface heat transfer capability of the reactor internals are studied in this paper. The surface temperature and heat transfer coefficient of the neutron shielding panels and the radiation surveillance capsules are investigated by scaled experiment and the numerical method under different injection conditions. The study found the dimensionless correlation between the wall surface temperature (and the heat transfer coefficient) and the injection flow rate conditions at several key points in the dangerous areas such as the top of the neutron shielding panel.