In order to investigate the spray combustion characteristics of the blends of butanol isomer and diesel and evaluate the practical application potential of different butanol isomers as diesel alternative fuel, a high speed camera was used to record flame developing process and the transient pressure sensor was used to record in-cylinder pressure to reveal combustion heat release rate under differnet ambient temperatures and oxygen concentrations for butanol isomer-diesel blends on an optical and visual test platform of constant volume bomb. These blends exhibited similar heat release law except at the temperature of lower than 800 K. In that condition, the combustion phase of n-butanol blends advanced significantly and its heat release peak increased at high oxygen concentration and they both changed in the opposite direction at low oxygen concentration. They showed the similar flame shape and developing process, but had slight difference in propagation timing. The flame lift-off length for them was almost the same at high ambient temperature and oxygen concentration and that of n-butanol blends increased obviously with showing the weak flame intensity at low temperature, which was beneficial to reduce soot emission. The butanol isomerdiesel blends exhibited similar heat release and flame developing characteristics, but n-butanol blends showed stronger potential on soot reduction as diesel alternative fuel at low temperature.