Abstract: The determination of the onset point of the oscillation was given in this paper. With experimental methods, the effects on the oscillation among singlephase tubes under different primary side inlet temperatures, secondary side flow rates and loop resistance coefficients were studied. The results show that as the primary side inlet temperature increases, the flow velocity at the onset point of the oscillation almost increases linearly. With the increase of the secondary side flow rate, the flow velocity at the onset point of the oscillation is almost constant. As the resistance coefficient increases, the flow velocity at the onset point of the oscillation first decreases and then tends to be stable. The small resistance coefficient mainly affects the flow velocity at the oscillation onset point, while the large resistance coefficient mainly affects the flow distribution. Additionally, it is found that the effects of the distribution of local resistance of the loop on flow distribution are negligible.