Based on a self-built optically visualized constant volume combustion chamber system，the effects of injection duration(3.0，6.0，8.6 ms)，injection pressure(30，40，50 MPa)，and ambient temperature(880， 910，940 K) on n-butanol spray flame were studied. The flame development process and combustion characteristics were revealed by flame self-illumination high-speed imaging method. Results show that the n-butanol spray flame shows a yellow-white flame as a whole，and there is a small amount of light blue flame upstream of the spray. Under small injection duration(3.0 ms)，a partial flame-quenching phenomenon presents after n-butanol ignites. As injection duration increases，the soot lift-off length shortens，and the flame brightness，ignition delay and combustion duration increase. As injection pressure increases，the flame brightness and flame backtracking phenomenon weaken，and the soot lift-off length increases. At the same time，the ignition delay is prolonged，but the combustion duration is shortened. The ambient temperature has a significant effect on the stable ignition of nbutanol spray flame. With an increase in ambient temperature of only 60 K，the ignition delay of n-butanol spray flame is notably shortened by 4.16 ms，while the flame brightness is obviously enhanced and the flame shape is more stable