Abstract: In order to solve the problems of the large field of view,high-precision and non-contact 3-D measurement in the complex environment,a trinocular measuring system was put forward,in which the 3-D coordinates of the measured point were measured by analyzing target images. When under the measurement,the camera captured images of the measurement target,while the computer obtained the 3-D coordinates of the mark points in the measurement target by means of image processing,and an optimized method for solving the measured points was proposed based on the distance between the measured points and mark points,as well as linear constraint. The measurement target can be moved with the platform of the high precision grating ruler and measurement can be carried out. As shown in the experiment,the 3-D measurement system has a greater improvement in the field range,measurement accuracy,operation flexibility and so on. Its measurement accuracy is higher than 0.2mm in the depth of field ranging from 2m to 5m within the viewing field.