The invention discloses a method for realizing lossless evaluation for damage performance of an optical element. A continuous laser device can transmit continuous laser. After a first energy regulator, a first lens, a reflector and the front surface of a sample, the continuous laser is irradiated to the back surface of the sample. The reflecting direction of the continuous laser after reflection by the sample is provided with a residual laser collector. The pulse laser can transmit pulse laser. After a second energy regulator, a beam compressing system, a split board and a second lens, the pulse laser is irradiated to the back surface of the sample. According to the method of the invention, multiple-sample and multiple-position testing is performed on the elements which are same with a to-be-tested optical element for obtaining a correlation relation between fluorescent defect data and a laser damage threshold and a damage density in the optical elements of this kind, thereby calculating the damage threshold and the damage density in measurement of the to-be-tested sample through measuring the fluorescent defect data. According to the method of the invention, a damage performance level of the optical element can be obtained through lossless testing for the fluorescent defect of the optical element, thereby realizing lossless evaluation to the damage performance of the optical element.