A transceiver with multi-wavelength coexistence is disclosed. A BOSA (bi-direction optical sub-assembly), a PCB (203) and a fiber receptacle (102) are disposed within a transceiver housing; the PCB (203) is horizontally arranged in the transceiver housing; the fiber receptacle (102) is disposed on the BOSA; the BOSA comprises multiple transmitters (0004) and multiple receivers (0003) all of which are optically coupled with the fiber receptacle (102) and electrically connected with the PCB (103); two or more BOSAs, which are stacked in parallel or perpendicular to the PCB (203), are disposed in the transceiver housing and respectively connected with an external fiber through multiple fiber receptacles (102).