Abstract: The forward LDV has wider applications than the backward LDV,because of its lower requirements of the laser power.In practical measurements,due tolimited circumstance,the backward LDV also must be used.In this paper,the light splitting system and the light receiving system of the different forward LDV have beenstudied,and an important method is provided to make forward LDV have the function to be used as backward LDV. The experimental results show the method is very well,so the method can be wide used in practical applications.