High-voltage power lines are often wrapped in plastics and kites which need to be removed in time, however the existing manual removal methods exist potential safety hazard. Taking the advantage of small divergence angle, good directivity and high brightness of laser, foreign matter can be effectively and contactless cleaned up. The laser damage test system has been built to measure the damage threshold of typical foreign matters. According to the results of the experiment, a fixed focal length beam emission system has been designed, which consists of three separate spherical mirrors with simple and compact structure. The length of the system is 272 millimeters, and the weight is 48 grams. The working distance of the system can be adjusted by changing the length between the laser source and lens. The system reaches the diffraction limit on the image quality. Base on the design, the system can remove foreign matters at distances from 20 meters to 200 meters through optimizing the distance from the source to the lens. Simulation result shows that a fundamental Gaussian beam emitted by the system at difference distance has a target diameter less than 9 millimeters, ensuring the effectiveness of the system.