Abstract: Control rod hydraulic drive system (CRHDS), which is invented by Institute of Nuclear and New Energy Technology, Tsinghua University for the nuclear heating reactor NHR200, is a new type of internal control rod drive technology. CRHDS is composed of control rod hydraulic drive mechanism (CRHDM), integrated valve, control rod and hydraulic buffer, etc. The cold state performance of CRHDS is the basis to determine control rod stepping time and system driving pressure. The composition and working principle of CRHDS were analyzed in the paper. The full scale CRHDS performance experiments, which include the minimum rod drop pressure test of hydraulic cylinder, step motion test of lifting cylinder and the scram performance test, were carried out under room temperature. Based on the experimental results, the changing laws of the key characteristic parameters of CRHDS were analyzed. The research results show that, the minimum rod drop pressure is the minimum driving pressure for CRHDM to work normally, and it corresponds to the starting point of the peak wave process on the time history curve of cylinder pressure. The inflection points of the pressure curves in the stepup and stepdown processes of the control rod correspond to the end points of the step motion respectively. With the increase of the driving pressure, the inflection pressure of the hydraulic cylinder increases gradually, the stepup time and the time of the turning point decrease during the stepup process. The experimental results lay the basis for the design, optimization and engineering application of the CRHDS.