Laser ranging technology is crucial for the monitoring and early warning of space debris. To improve the monitoring capability of the 1.2 m telescope laser ranging platform of the Yunnan Observatory of the Chinese Academy of Sciences for space debris, the daytime laser ranging technology and method for space debris monitoring were studied. First, the feasibility of using the existing 1.2 m telescope laser ranging platform of the Yunnan Observatory to perform daytime space debris laser ranging was analyzed. Then, the key problems associated with space debris laser ranging during daytime were analyzed and solutions were proposed. Based on a daytime space debris laser ranging experiment, some space debris laser ranging data were obtained. The cross section of the measured space debris radar ranges from 9.0 m² to 20.0 m², the perigee ranges from 400 km to 900 km, and the apogee ranges from 500 km to 900 km. Results show that the space debris laser ranging platform of the Yunnan Observatory can perform space debris laser ranging during daytime, which can provide technical support for subsequent research on space debris laser ranging.