Trapezoidal distortion correction and clear images collection are important indexes of an optical fingerprint identification system. Total internal reflection acquisition method of surface light source is adopted and cheap k9 glass is chosen as the material of prism. Three pieces of spherical lens is used as an imaging system in which two pieces of small lens can be designed into the same lens by optical design software CODEV. The whole field of view of optical modulation transfer function (MTF) is more than 0.5. There is no trapezoidal distortion and illumination is uniform. Comparing with other non-trapezoidal distortion productions on market, the product has smaller volume and lower cost. It is easy to fit and can meet the needs of production.