Uncertainties for thermal protection efficacy caused by deviations of the values of phase change materials (PCMs) properties (including conductivity, heat capacity, thermal conductivity, latent heat and phase transition temperature) were studied based on our previous study. Our results suggested that the radius of the micro/nano PCM particle, and the upper and lower phase transition temperatures of the PCM should be carefully measured before performing thermal protection by PCMs during hyperthermia. The results will further help us to enlarge the application of clinical hyperthermia in cancer treatment and optimize the treatment protocol of thermal protection by PCMs.