A new method for spray combustion simulation was proposed in which the state of a droplet is divided into two modes: the combustion mode and the evaporation mode. The combustion mode assumes single droplet combustion, and the evaporation mode assumes group combustion or evaporation. First, single droplet combustion analysis was carried out and a database of evaporation rate, flame radius and heat transferred into the droplet was prepared. Evaporation rate in the combustion mode was calculated from the database, and evaporation rate in the evaporation mode was calculated with a conventional evaporation model. In this study, a simulation of heavy oil spray combustion was carried out, and the calculated results were compared with experimental findings. The result showed that it is possible to calculate heterogenous combustion, suggesting that our method is effective for spray combustion simulation of low-volatility fuel.