A one-way drive strap wrench has a handle, a threaded rod module mounted in the handle and a clamping module mounted in the handle. The clamping module has an asymmetric clamping block and a strap. The clamping block is mounted around a combining unit of the handle and has an accommodating trough accommodating a pushing segment of the threaded rod module, wherein the accommodating trough is wider than the pushing segment. The strap is circled around the clamping block to form a surrounded area. A crossing angle is formed between the axis of the handle and the blocking line and is smaller than 90 degrees.