The growth power-time curves of three strains of petroleum bacteria (B-1, B-2 and B-3) are determined by using a 2277 thermal activity monitor. A kinetic equation of bacterial growth in limited conditions is used. The equation of describing the power-time curve is derived. The growth rate constants at different temperatures up to 56 degrees C, salinities up to 10.0 (g/100 ml) NaCl and pH ranging from 6.08 to 7.74, are calculated. The lowest growth temperature, optimum growth temperature, highest growth temperature, optimum growth salinity and optimum growth acidity have been obtained, which are 29.1 degrees C, 50.7 degrees C, 54 degrees C, 1.48 and 7.15 respectively for B-1, 28.5 degrees C, 51.4 degrees C, 56 degrees C, 2.38 and 6.91 respectively for B-2, 26.8 degrees C, 50.7 degrees C, 56 degrees C, 3.55 and 7.11 respectively for B-3.