Abstract: Based on a multi-purpose small nuclear reactor (NHR) developed at Tsinghua University, a natural circulation experimental loop to study the characteristics of natural circulation under rolling condition with zero power was built. The effect of rolling angle ψ_m and rolling cycle T of single-freedom rolling motion on natural circulation was explored through the analysis of several groups of experimental results, and the linear relationships between flow amplitude V_o and rolling motion parametres ψ_m and T were given. The results indicate that the obvious influence of rolling angle ψ_m on flow velocity of two-side channels of heating section is observed, and flow velocity wave amplitude V_o increases with ψ_m. V_o decreases with the increase of T, and the wave phase of flow velocity fluctuation is unrelated with T. In rolling condition with zero power, a linear relationship between the V²_o and the product of ψ_m, the square of frequency w²_d and the equivalent rolling radius R_eq is proved.