Rapidly obtaining the three-dimensional error information for all tooth surfaces of gears is the key and prerequisite for characterizing the quality of complex tooth surfaces. In this paper, based on the principle of laser triangulation, a three-dimensional measurement model with line laser is established for the gear, and the developed measuring instrument can be used to quickly obtain the error information of three-dimensional tooth surface and evaluate the quality of gear. The instrument adopts the vertical structure consisting of base, precision spindle, circular grating sensor, control system and software system, etc. The precision spindle adopts the dense bead shaft system to achieve high-precision rotation, which ensures the high-precision positioning and rotation of measured gear. Two high-precision line laser sensors are arranged in the circumferential direction of the precision spindle, and the positional state is adjusted according to the parameters of measured gear. Specifically, the rotation angle of precision spindle is acquired by the circular grating in real time, and the geometrical information of gears’ left and right flanks is collected and recorded by the collector in real time. In conclusion the three-dimensional measurement and evaluation software for the gear has been developed, which can realize the measurement and evaluation of gear′ s tooth profile deviation, pitch deviation, topological deviation etc. , and meet the detection requirements of grade 5 precision gear Ke . ywords:gear; gear measurement; gea