In this study, a novel high temperature two-phase closed flat heat pipe receiver is proposed and investigated experimentally. In order to simulate the transient startup from frozen state, a transient analysis code for the novel flat heat pipe receiver has been developed. Closed-form analytical solutions for the temperature distribution along the heat pipe length are obtained and experimental tests are undertaken. These closed-form analytical solutions are in good agreement with the experimental data. The theoretical and experimental studies prove that the flat heat pipe receiver with sodium as working fluid has a well startup performance. Experiments were carried out to investigate the temperature uniformity of FHPR under the normal conditions. It is found that the FHPR has well feature of uniformity and stability through startup process experiments with constant heat flux. This research provides guidance for the research and development of flat heat pipe solar receiver, and has important significance for broadening its application in the field of heat utilization of solar energy at high temperature. (C) 2019 Elsevier Ltd. All rights reserved.