Abstract: In order to investigate the transmission efficiency of movable-teeth CVT(MCVT), the power losses of MCVT was analyzed and the theoretical model of its transmission efficiency was set up. Then, transmission efficiency test platform was set up for the MCVT. Lastly, experimental study of the relations among transmission efficiency, speed and torque was conducted when the transmission ratio was fixed.The results show that the power losses of the sliding friction and impact caused by the backlash of the tooth, the power loss of the oil stirring and the power loss of oil seal are the main power losses of iMCVT.The transmission efficiency of iMCVT can reach 95% when the constant transmission ratio is 1.2.Torque is the most significant impact to the transmission efficiency.The effect of speed on the transmission efficiency of iMCVT is not significant,but the efficiency of high speed is greater than that of low speed.The transmission efficiency is gradually increasing when speed and torque both range from the low to high.