Optical coherence tomography （OCT） technology has the advantages of non-invasive， high-resolution， and real-time imaging， which is widely used in various fields such as biomedicine， material science and infrared sensing. A ridge suspended optical waveguide based on silicon nitride （Si₃N₄） is proposed. The structural parameters of the designed waveguide were optimized by using finite difference time domain （FDTD） method. The characteristics of the supercontinuum spectrum generated in the optimized waveguide were investigated The simulation results show that for the optimized optical waveguide structure with ridge width of 750 nm， ridge height of 700nm， plate thickness of 200 nm， and upper layer height of 150 nm， when a pump light with wavelength of 1.3μm， peak power of 2 kW and pulse width of 50 fs was injected into the waveguide， a broadband supercontinuum spectrum with wavelength covering the visible to the mid-infrared region （703~4014 nm） can be generated. This work plays an important role in promoting the application of on-chip integrated broadband light source in biomedical imaging and related fields.