An internal crack is a common defect which can lead to failure of the material. There are few published studies which can quantitatively predict healed fractions under given conditions such as temperature, pressure and healing time. In the current study, a new crack healing kinetic model is developed to predict the healed crack fraction under any given temperature, pressure and healing time. In contrast to previous models, this new model describes the crack surface topography as a series of semi spherical pores, and proposes a new diffusion healing mechanism involving grain growth. Plastic deformation, power law creep and diffusion controlled creep mechanism are considered in this model. A crack healing diagram for 34MnV steel is constructed with axes of healed fraction and temperature or pressure. The predictions from the new model compare well with experimental results. The results of the model indicate that the diffusion controlled creep mechanism contributes little at high temperatures because of grain growth. The critical healing time and pressure can be determined by using the crack healing diagram.