A new approach is described to detect the position status of collimating mirror with a shearing interferometer based on micro-wedge. Laser beam having the same divergence as the synchrotron radiation can be created with a lens and a pinhole, and by measuring the parallelism of the laser beam reflected by the collimating mirror with the shearing interferometer, the best status of the collimating mirror about its position, pitch, curvature and bending force can be determined. This interferometry scheme is easily aligned, every interference pattern corresponds with only one status of the collimating mirror. Therefore this approach can determine the whole status of the mirror. The approach is especially fit for measuring the wavefront with small output width but long curvature radius, and not only has high accuracy but also is valuable in practice.