Using isothermal microcalorimetry, the growth power-time curves of three strains of Tetrahymena were determined at 28C. Their Euclidean distances and cluster analysis diagram were obtained by using two thermokinetic parameters (r and Qlog), which showed that T. thermophila BF1 and T. thermophila BF5 had a closer relationship. Compared with the single molecular biomarker (ITS1) method, microcalorimetry wasmaybe a simpler, more sensitive andmore economic technique in the phylogenetic studies of Tetrahymena species.