The temperature of hot electrons produced in ultra-short ultra-intense laser-plasma interactions could be measured by photonuclear diagnostic method. In this paper, the process of bremsstrahlung gamma photons generated by hot electrons interacting separately with 63Cu, 107Ag, and 12C, were simulated using the Monte Carlo N-particle transport code (MCNP). According to the different cross-sections, the activities of different samples were calculated. The activity ratios for 11C/62Cu and11C/106Ag were achieved at different electron temperatures. This method can realize the temperature diagnostic of hot electrons in laser-plasma interactions.