To solve the problem that a methane telemetry device can not be dynamically adjusted when it is used in different detection environments due to its fixed optical collimation, an electronically controlled zoom lens is introduced into the optical path collimation design to achieve automatic optical path collimation. Test results show that for different detection distances and auxiliary targets, the fast zoom can be achieved by changing the driving current of the electronically controlled zoom lens. The receiving optical power of the telemetry device can be maximized while dynamically adjusting the laser beam divergence effect. Compared with the non-zoom lens, the receiving optical power can be increased by more than 1.7 times, and the signal-to-noise ratio of the detection system is improved. In view of the new problems of the zoom lens in telemetry applications, such as beam deflection caused by the gravity effect, a deformation model is proposed, and theoretical calculation and simulation analysis are carried out. A methane gas bag is used to conduct a leak simulation test. Through the Allan variance analysis, we obtain that when the integration time is 18 s, the limit standard deviation is 1.51×10 ^-6. The field measurement for the device is conducted, the test distance is 52.2 m, and the methane gas with the concentration (volume fraction) of 4.95×10 ^-6 is detected in the corridor air. The research demonstrates the feasibility and the application value of using an electronically controlled variable focus lens to realize automatic collimation and optimization of the optical path in a gas leakage telemetry device.