Abstract：The ignition and combustion characteristics of n-heptane, oleic acid/n-heptane mixed fuel, and Al?oleic acid/n-heptane-based nano-slurry fuel droplet which contains 20wt% nano-sized Al powder at different temperatures (600~800℃) were studied by a droplet suspension method. A high-speed camera was used to observe the ignition and combustion process of these droplets when the droplets were placed into the tubular resistance furnace. The temperature changes of gas phase around the droplets were recorded by a thermocouple, and the ignition delay times of the droplets were calculated according to the obtained temperature curves. The results showed that the additions of nano-sized Al powder and oleic acid into the n-heptane reduced the ignition delay time of n-heptane droplets. With the ambient temperature increase, the ignition delay times of n-heptane, oleic acid/n-heptane mixed fuel, and Al–oleic acid/n-heptane-based nano-slurry fuel droplets all decreased significantly, but the trend gradually became flat. The relationship between the ignition delay time of Al-oleic acid/n-heptane-based nano-slurry fuel droplet and the ambient temperature were described by the Arrhenius equation. Compared the combustion of Al?oleic acid/n-heptane-based nano-slurry fuel droplet with n-heptane and oleic acid/n-heptane mixed fuel droplets, the combustion process of Al?oleic acid/n-heptane-based slurry fuel droplet had significant difference. The combustion of Al?oleic acid/n-heptane-based nano-slurry fuel droplet had three stages: stable combustion stage of n-heptane, micro-explosion stage of n-heptane and micro-explosion stage of surfactant. Especially, the combustion process of Al?oleic acid/n-heptane slurry fuel droplet had long combustion time, and the flame was extinguished and re-ignited. In addition, the combustion process accompanied the severe flame deformation and sputtering of Al particles. In micro-explosion stage of surfactant, most of nano-sized Al powder form the agglomerates, then the formed Al agglomerates occurred redox reactions and burned completely.