Abstract: Aiming at the status that mostly available methods for relative orientation are used for stereo images with the same focal length, in order to make full use of image information photographed by different cameras, with image point coordinates under correction, coplanarity equation is strictly linearized by computer algebra system, and strict solution for relative orientation of image pair with different focal lengths is carried out. Finally, the correctness of the formulae is verified by numerical examples. This method could enrich theories of photogrammetry to some degree.

Key words: photogrammetry, stereo images, relative orientation, coplanarity equation, linearization