Based on the principle of non-imaging optical edge light and the law of geometric optical reflection, the mathematical model of the surface structure of compound parabolic concentrator (CPC) without gap loss is constructed for circular absorber, and the numerical solution of the equal-length reflector is obtained by program calculation. The CPC model without gap loss is verified by a visible laser experimental device, and the results show that the light path calculated by numerical method is consistent with that of laser experiment. Moreover, the CPC without gap loss of a single pair of equal-length reflectors has the largest length of a single equal-length reflector, which is exactly the radius of the absorber. When the number of equal-length reflectors increases from single pair to 6 pairs, the length of a single equal-length reflector decreases from 23.50 mm to 7.65 mm. In the process of practical application, the number of pairs of equal-length reflectors should not be too much.