A calculation method suited for spray combustion with compressible flows in a jet burner and the effect of soot on radiative heat transfer in the burner were investigated. In addition, the effect of air ratio on the combustion behavior was also discussed. Numerical stabilities were improved by using the compressible form of SIMPLER algorithm. When soot formation and radiation is solved, the calculated peak temperature decreases by 134.2 K. Therefore, it is important to calculate soot concentration accurately. When the air ratio decreases, the high temperature region extends to downstream because the mixing of spray and air deteriorates. The extension of the high temperature region results in the increase in NO concentration. Therefore, the improvement of the mixing of spray and air is effective in reducing exhaust NO concentrations because the high temperature region becomes smaller and shifts upstream.