Abstract: With the large-scale application of 5G and artificial intelligence, the optical module will develop to high speed and low price in the future. Based on the above requirements, this paper proposes a 400G FR4 silicon photonics optical transceiver module design, develops core photonic devices. The module uses a silicon-based electro-optical modulator to achieve high-rate optical signal modulation, and is paired with wavelength division multiplexing and demultiplexing devices to further increase the overall transmission rate of the module, and verifies that the device performance meets the design requirements. The optical path of 400G FR4 optical module has been designed with the method of Chip On Board (COB) packaging technology, and the coupling efficiency from the laser to the modulator can reach −2.1 dB, achieving low-loss coupling between various optoelectronic devices, which provides a guidance for the design of 400G optical module.