The working process of the semiconductor photoelectric position sensitive device is analyzed. Using the continuous sending laser light source and semiconductor photoelectric position sensitive device, a high accurate tri-dimensional non-contact optical measurement system is designed. With the gridlines of the rectangular coordinate system located on the object being measured, the outline of the object is produced by this system, then it is applied to the measurement and diagnosis of multi-parameter of the irregular tri-dimensional object. Consisting of optical arrangement, this system is suitable for accurate measuring and detecting of the figures with irregular shape especially the edge shape. The tested datum has high value for studying and diagnosing the relationships of the skin lesion's format, character and type. The system will be used widely in the future.