In order to research the influence of cooling oil temperature on cutting stability of machine, continuous trial cutting experiment was carried out with gear shaping machine. The distance of bar of each sample was measured. The cutting stability was evaluated by the fluctuation amplitude of relative difference and standard deviation at different temperatures. The machine capability index was calculated and the level of the stability of its precision was assessed quantitatively. The results show that the fluctuation amplitudes of relative deviation and standard deviation are smaller when cooling oil temperature is 33 ℃. And the cutting stability of gear shaping machine is better. The requirements of high precision processing cannot be researched owing to a sharply falling of cutting stability when the cooling temperature is over 40 ℃. The conclusion provides reference for improving stability of machine in actual production.