A novel high step-up interleaved DC-DC converter with ZVZCS is proposed. Based on the coupled-inductor and switching-capacitor topology, this converter is designed by combining interleave technique and active clamp together, which can realize soft switching and high output power in the same time. During steady-state modes, the leakage inductance will resonate with two switching capacitors. Under different resonant frequencies, ZVS and ZCS can be realized for certain switches and diodes, respectively. Therefore, the switching loss and reverse recovery are alleviated, which improves the efficiency of the converter. In addition, the mode boundary map for distinguishing soft-switching modes are derived and depicted. A prototype with 24 V input voltage, 400 V output voltage and 800 W output power is implemented in the laboratory to verify the performance of the proposed converter.