The monolithic photonic integrated circuit (PIC) is the core component in the fu ture high-capacity,low-power consumption optical network systems.As a typical photonics integrated device,monolithically integrated multi-wavelength distribu ted feedback (DFB) laser array plays an important role in dense wavelength divis ion multiplexing (DWDM) optical transmission systems.The monolithic integration of four distributed feedback lasers with a 4×1multimode-interference (MMI) o ptical combiner and semiconductor optical amplifier (SOA) using varing width rid ge method and butt-joint technology is proposed and demonstrated in this paper. The monolithically integrated chip is 2500μm long and 400μm wide.The active and passive materials are integrated by the butt-joint tec hnique,and the varing ridge width is used to adjust the effective index of the l aser material,so that multi-wavelength emission can be achieved by normal holog raphic exposure.This method is simple and practical.The integrated device is tes ted at 25° for characterization.The average output power of 2mW is achieved wh en the current of LD and semiconductor optical amplifier (SOA) is 150mA and 50mA,respectively.The threshold current of the device is 55－60mA at 25℃.The la sing wavelength is around 1550nm and more than 33dB sidemod e suppression ratio (SMSR) is obtained.The four channels can ope rate separately or simultaneously.