The traditional DC/DC converter has some shortcomings, such as limited voltage gain and large voltage stress on switching tubes, diodes and other devices. An asymmetric cross-parallel high step-up DC-DC converter is proposed. On the basis of the second type Boost circuit, the switching inductance three-terminal network is introduced to form the asymmetric cross-parallel circuit, which raises the gain of the converter and reduces the voltage stress and current stress on the components. The gain of the converter is further raised by introducing the switching capacitance into the three-terminal gain circuit. The operating modes of the converter under different duty cycle are analyzed in detail, the DC steady-state model of the circuit system is established, and the steady-state voltage gain of the circuit is derived. Finally, the correctness of the scheme is verified by Matlab simulation and experiment results. This work is supported by National Key Research and Development Program of Hebei Province (No. 18214302D and No.16211806D).