Methanol fueling can make diesel engine achieve efficient and clean combustion. The evaporative properties of the fuel have a significant effect on the mixing, ignition and combustion process. Methanol has a low cetane number, which makes ignition difficult. The cetane number of methanol fuel can be increased by the addition of n-heptane. the droplet evaporation process of n-heptane methanol droplet was studied based on image processing technology by using the single droplet hanging measurement method and high-speed camera to capture the droplet evaporation image. The effects of different n-heptane blending volume ratios (0, 5%, 10%, 15%) and ambient temperatures (100-500 ℃) on the evaporation characteristics of droplets were analyzed. The results show that the evaporation characteristics of n-heptane-methanol droplet followed the D2 law, which means that the square of the ratio of the droplet diameter D to the initial droplet diameter D0 ((D/D0)2) is linearly related to the evaporation time. The trend of the relative area of the droplets with time is approximated as a straight line with a negative slope. The evaporation rate of droplets increases with the increase of temperature when the mixing ratio is fixed. The evaporation rates per unit area of droplets is increased by 543%, 639%, 896%, and 556% for 0, 5%, 10%, and 15% n-heptane blending ratios, respectively, when the temperature is increased from 100 ℃ to 500 ℃. The evaporation trends of methanol droplets with different n-heptane additive blending ratios are basically the same when the temperature is certain. Compared with pure methanol, 5% volume ratio of n-heptane prolongs the evaporation time of droplets except at 200 and 300 ℃. At 100 ℃, the droplet evaporation time is shortened with the increase of n-heptane blending ratio, while prolonged at 200 ℃. At the rest of the test temperatures, the droplet evaporation time is prolonged and then decreased with the increase of n-heptane blending ratio. At 200, 300, 400 and 500 ℃, the droplet evaporation time is prolonged by 53.9%, 17.1%, 47.5% and 53.1% when the n-heptane blending volume ratio increases from 5% to 15%, respectively.