1. A projected moiré fringe 3-D surface shape measuring device the characteristics of device are that the said device includes a projection device with mark point and main grating, and an observation device with mark point and sub-grating, as well as two coordinate rectilinear motion axes which form a right triangle consists of the mark point of projection device in the imaging position, the mark point of observation device, and the mark point projected on object surface by projection device.