Whispering Gallery Mode (WGM) microcavities exhibit ultrahigh Q factors and extremely small mode volumes, along with weak backward Rayleigh scattering. By utilizing this feedback mechanism in WGM microcavities, a laser linewidth compression by several orders of magnitude can be achieved, based on which a narrow linewidth laser is designed. Numerical simulations were used to analyze the optical behavior during the self-injection locking process, specifically the effects of changes in phase, detuning, backscattering and coupling efficiency on the system performance. Additionally, experimental validation is performed using a semiconductor laser with a central wavelength of 1552.126nm, and the 7 MHz linewidth laser output was narrowed to 500 kHz in the experiments. The narrow linewidth laser achieved through this approach has many advantages such as lightweight, high convenience, and stable performance. As a result, this narrow linewidth laser holds potential applications in areas such as laser interferometry, laser gyroscopes, laser ranging, and other related fields.