The effect of the deformation temperature, deformation degree, strain rate and their interaction on the microstructure and mechanical properties in the high temperature deformation of Ti-6Al-4V alloy was investigated. The experimental results show that the deformation degree and strain rate have significant influence on the microstructure and mechanical properties, in which finer microstructure and higher tensile strength can be obtained at a middle deformation degree and a higher strain rate. The interactions between the deformation temperature and the deformation degree or the strain rate in the high temperature deformation of Ti-6Al-4V alloy are significant, especially being deformed at the temperature just under the β transus, the ductility and tensile strength are sensitive to all of processing parameters including their interactions. So the interactions should be considered to optimize the processing parameters in order to meet the requirements of the mechanical properties.