Abstract: A control method of radon progeny state parameters in small radon chamber was established based on behavior theory of airborne radon progeny and aerosol particle. The state parameters including radon and radon progeny concentration, equilibrium factor and unattached fraction were controlled steadily in small radon chamber by adjusting the total ventilation rate of radon chamber and aerosol particle number concentration. Physical model of the control method was established, and the behavior parameters of radon progeny and aerosol particles were selected considering the simulation condition. The control range was calculated by Matlab program, and the physical model was partly verified by inter-comparing theoretical results and experimental data achieved by radon laboratory of University of South China. The inter-comparing results prove that the control method constructed in this paper is applicable, and the control method provides a preliminary theoretical foundation for the control experiment of radon progeny state parameters in small chamber.