The invention discloses an on-chip integrated optical digital-to-analog converter based on a silicon-based nanowire waveguide. The on-chip integrated optical digital-to-analog converter comprises N laser devices, a modulation multiplex integral structure and a photoelectric detector. The modulation multiplex integral structure comprises a trunk waveguide L0, N cascaded silicon-based nanowire waveguide micro-ring resonators (MRR1, MRR2...MRRN) and N bent waveguides (L1, L2...LN), the N laser devices are connected with the uploading ends of the N bent waveguides (L1, L2...LN) respectively, the photoelectric detector is connected with the straight-through end of the trunk waveguide L0, and N is a natural number. According to the on-chip integrated optical digital-to-analog converter, the advantages that the silicon-based waveguide is compact in structure, low in power consumption, compatible with the CMOS process and the like are fully achieved, the high speed and high resolution in the DAC process can be achieved, and the integration and miniaturization of the optical DAC can be achieved.