Abstract: The safety rods of China Advanced Research Reactor (CARR) are driven by the hydraulic force. The test showed that a series of problems for the earliest fabricated 2 sets of the drive mechanisms were found in the aspects of the design and the fabrication, so many times of the stuck rods were happened during the out of pile test. Through the improvement of the design and fabrication, the validation test indicates that the performance of 2 sets of new drive mechanisms is very good.