A two-dimensional cellular automaton model is developed to simulate the isothermal hot compression phase transformation of β→α in TA15 titanium alloy. The model, based on the data of hot compression deformation and some assumption, the phase transformation nucleation and growth function of the phase β→α which is utilized by the automaton in a probabilistic fashion. The probability of nucleation and growth of α phase is confirmed and described by the existing theories of dislocation density. The competition between phase transformation and growth of transitional phase is described by the changes of dislocation density in this cellular automaton lattice. Based on the results of cellular automaton, the transformation fraction of α phase is calculated with the number of lattice and isothermal phase transformation kinetic equation is also calculated with data of transformation fraction, and the effect of hot compression deformation parameters on phase transformation is also discussed.