In order to study the height characteristics of fire whirls in a vertical channel, experiments of fire whirls induced by ethanol and Nheptane in different diameter fuel pans were performed in a vertical channel with a dimension of 32 cm (length) ×32 cm (width) ×200 cm (height) and corner gaps, opposite gaps, respectively. In the experiments, the flame height reached its maximal stage after a relativelyshort primary stage. The later height of stronger fire whirls induced by Nheptane dropped rapidly, but for ethanol, there existed a buffer stage. For stronger fire whirls induced by N-heptane, both buoyancy and violent rotating had an obvious effect on flame height. The dimensionless expression for flame height was revised based on the results of experiments.