The advent of third-generation semiconductors brings the switching frequency into a much higher level, which enables high-frequency transformer with a smaller footprint in power electronics. Due to its inherent ability of voltage amplification, the transformer-based voltage-multiplier becomes prevalent in step-up converters which are the inevitable parts in the usage of low-voltage renewable resources. Though its feasibility has been verified in many researches, an uncertain error in voltage conversion ratio exists between the reality and ideal, which leaves a theoretical gap. Accordingly, the key affecting characteristics, the reverse recovery process of the leakage inductance, is considered and analyzed in this paper. The power transmission mechanism is clarified, and the root-mean-square error of the gain can be reduced from 24.31% to 3.13% , and the maximum output power together with power effect on the gain are obtained. With the conclusion of this paper, parameters of power supply can be optimized at the beginning of design to satisfy the demand of maximum output power and gain over a wide power range, which can save the unnecessary trial-and-error during the case-by-case design.