Chip-scale narrow-linewidth lasers have rich applications in sensing, communication, spectroscopy and light detection and ranging (LiDAR). Self-injection locking is one of the most efficient techniques to reduce linewidth significantly. By locking a laser to an external cavity, some amounts of light reflect back into the laser for mode competition, leading to a significant reduction of the lasing linewidth. In this work, we demonstrated a hybrid-integrated laser with a microring resonator (MRR) butt-coupled to a distributed feedback (DFB) laser. The radius of the MMR is designed to be 442.3 μm, corresponding to a free spectral range (FSR) of about 50 GHz. And the MMR has a quality factor (Q factor) of 3×10 6 , fabricated in an ultralow loss silicon nitride (Si3N4) waveguide platform. In this way, the frequency noise has been reduced to 12.565 Hz²/Hz at the 10 MHz offset frequency. Finally, 40 Hz intrinsic linewidth and 91.2 kHz integral linewidth are achieved, characterized by a delayed self-heterodyne interferometer.