In order to meet the demands of surface shape measurement in trough solar thermal power generation, a fast surface shape measurement technique for trough solar concentrators based on deflectometry principle is proposed after investigating the current research situation in detail. A self-iterative algorithm is used to reconstruct the surface shape and the photogrammetry method is adopted to calibrate the position of the measured concentrators. It makes this measurement system simpler and faster to operate and suitable for online test. The measurement principle of this technique is introduced and the testing platform is built. A piece of parabolic trough solar concentrator is measured. The experimental results indicate that the qualitative surface shape data of the measured mirror can be worked out quickly by using this method. And the feasibility and correctness of this method are verified.