For the problem of searching radioactive sources in a certain area, a search method combining Tsallis divergence strategy with a particle filtering algorithm is proposed. The method this paper proposes for searching for radioactive sources is carried out by using a mobile platform equipped with a NaI(Tl) scintillator detector. The estimation model of the parameters of the radioactive source is constructed and is based on the inverse square law and the fact that the count values of the NaI(Tl) detector in nuclear decay processes obeys the Poisson distribution. The Tsallis divergence strategy is used as a reward function to control the movement of the platform. The posterior distribution of the parameters of the radioactive source is continuously and iteratively updated by using the particle filtering algorithm. The results of Monte Carlo simulations and practical experiments verify the effectiveness of the algorithm.