Abstract: This paper proposed the concept of the remained divergence angle of Scotchlite retroreflector, and designed the testing system. The laser beam was transmitted to the Scotchlite retroreflector, the reflected laser beam was imaged on the sulfuric acid paper（equivalent to receiving screen）, and the image data of the laser spots at different distances were captured by using a camera. In order to calculate the remained divergence angle, a program for corresponding image data was written. Experiment results showed that the remained divergence angle of Scotchlite retroreflector used in the test was 0.447 8.