The space optical remote sensor will generate the out of focus which leading the decrease of the quality of the remote sensor imaging,so a focusing mechanism is designed to solve the problem. In order to ensure the remote sensor imaging quality and the perspective of light miniaturization,the focusing scheme,working principle and system composition are introduced particularly,and then the double-slider mechanism is proposed to realize the focusing function. The position precision and focusing mirror tilt angle error can satisfy the requirement of the design index by the theoretical calculation to get the precision of the focusing mechanism. The data before and after testing indicate that the displacement error is less than 0.006 mm and the line tilt is less than 16.5″,which meets the requirement for use. Theoretical calculation and experimental results prove that this focusing structure has stable structure,high positioning accuracy,environment adaptability extensive features to meet the purpose of precise focus of space optical remote sensor.