Abstract: The precision of pulse laser ranging is the key factor of two-dimensional laser scanning imaging. It is very important to develop pulse laser ranging technology of sending and receiving coaxial optical system in indoor instance to improve the capability of two-dimensional laser scanning imaging. Relationship between the precision of pulse laser ranging and the laser echo energy was analyzed by simulation. The basic design scheme of optical system of the two-dimensional scanning imaging were proposed. In indoor instance, the nonlinear relationship between the laser echo energy and range of sending and receiving coaxial optical system was calculated and the nonlinear curve between the laser echo energy and range was delineated. Finally, the nonlinear relationship was verified by the actual test data and the effect of the nonlinear relationship on the precision of pulse laser ranging was analyzed. The study of thesis has important value in the design of system of laser ranging and the conclusion can be applied to perfect the design of optical system of pulse laser ranging in indoor instance.