Experimental study has been conducted on the occurrence of boilover processes in the pool fire. The flame and water temperatures and optical energy were measured during the pool burning of hydrocarbon with high boiling point. n-Hexadacane layer with emulsion layer were composed on the water sublayer in the cylindrical container. Attention was mainly paid for temperature conditions at the occurrences of boilover in the pool burning processes. It is concluded that the time for extinguishment become to shorten by existing of emulsion layer, in which boilover processes were largely changes. Occurrence conditions of boilover were also discussed by time histories of flame, emulsion layer and water sublayer with optical energy from pool fire.