The deformation behavior and microstructure evolution after isothermal near β deformation of TA15 titanium alloy with initially equiaxed microstructure were investigated by compression tests. The effects of deformation temperature, strain and strain rate on the deformation behavior and microstructure transformation were quantitatively characterized through metallographs analysis. Results show that dynamic recrystallization is suppressed and dynamic recovery is promoted with the deformation temperature increasing or the strain rate decreasing. Otherwise dynamic recrystallization is promoted and dynamic recovery is suppressed with the deformation temperature decreasing or the strain rate increasing. Deformation temperature is the primary factor influencing the volume fraction, the size and the aspect of equiaxed α. Increasing strain rate has little effect on the refinement of equiaxed α. The empirical model was developed to describe the relationship between deformation temperature and the volume fraction as well as the size of equiaxed α in the near β temperature range. The research results can provide a guide for process optimization and control of isothermal near β deformation of TA15 titanium alloy