Abstract: Firstly, based on the analysis of the operating principle of interleaved tri-state Boost converter (ITBC), the small signal model of ITBC was established. By deriving the control-output transfer function, the influence of different freewheeling control strategies on the right half plane (RHP) zero point of ITBC was analyzed. Secondly, based on the analysis of the factors that affect the magnitude of input current ripple, this paper divided the operating mode of ITBC, deduced the corresponding expression of input current ripple, and researched the relationship between input current ripple and duty ratio of inductor-discharging interval. Thus, by increasing the duty ratio of inductor-discharging interval, the operating mode of ITBC can be changed and the input current ripple can be reduced. Thirdly, the peak current fixed off time control strategy was adopted, which can meet the current sharing effect of inductor current and ensure that it operates in the mode of minimum input current ripple in wide load range. Finally, the correctness of theoretical analysis is validated by simulation and experimental results.