The invention discloses a realization method of an I2C bus for a multi-hardware platform FT server. The method comprises the following implementation steps of: 1) designating two spare general purpose input/output (GPIO) ports in a peripheral component interface express (PCIe) exchange unit as I2C bus interfaces, and connecting the GPIO ports to an upwards pulling resistor respectively; 2) when hardware is initialized, mapping a peripheral component interface (PCI) memory space of the PCIe exchange unit as a central processing unit (CPU) virtual address space; 3) acquiring mapping port addresses of the two GPIO ports in the CPU virtual address space according to the type information of the PCIe exchange unit; 4) establishing a GPIO driving program of the two GPIO ports; and 5) when I2C equipment is used, performing communication between an instruction of an I2C bus time sequence generated by an I2C bus controller driving program and the I2C equipment through the GPIO driving program. The method has the advantages of capability of utilizing the spare GPIO ports, low implementation cost, simpleness in implementation, convenience in use and high compatibility.