By employing a fiber-coupled diode-laser as the pump source and a 5 mm long cesium vapor cell as laser media, the experiments on the mode-matching of a LD-end-pumped cesium vapor laser were investigated. The effects of the focus spot radius and the position of focused pump light on the output characteristics of cesium laser were analyzed. Then, the different mode-matching parameters were optimized to allow the slope efficiency and optical-to-optical efficiency to be maximal. Furthermore, the threshold pump power of the laser was studied. Results show that there is an optimal focused spot radius to allow the slope efficiency to be the highest when the laser resonant mode beam is constant. Moreover, it is beneficial to improve the efficiency when the focused spot position is in the center of vapor cell. The threshold pump power was also researched, which shows the power can decrease with decreasing the focus spot radius of pump light, and when the pumping light focuses on the front of the vapour cell, the pumping power can be reduced. Finally, a series of parameters were optimized at the laser mode waist of 167 μm, and they are focused spot radius of 333 μm, spot position of 2.5 mmm and the focusing position of pumping light on the center of the vapour cell.KRUPKE W F,BEACH R J,KANZ V K, et al.. Resonance transition 795-nm rubidium laser［J］. Opt. Lett., 2003, 28(23): 2336-2338.