The invention discloses an audio noise reduction accelerator system and method based on RISC v custom instruction set expansion, and belongs to the technical field of integrated circuits. The system mainly comprises an E203_CORE, an NICE_CORE, a NICE_Interface, an E203_SOC, an audio coding and decoding WM8731 module, and an audio noise reduction FxLMS algorithm, wherein the E203_CORE is connected with the NICE_CORE through the NICE_Interface, the E203_CORE, the NICE_CORE and a related peripheral port form the E203_SOC together, the E203_SOC is connected with the audio coding and decoding WM8731 module, and the audio noise reduction FxLMS algorithm is downloaded into a core of the RISC v processor through software programming to run. Compared with a processor of an ARM instruction set architecture, the processor adopting an RISC v custom instruction set can accelerate a specific operation part in the audio noise reduction FxLMS algorithm; and the problems of area, power consumption, granularity and the like can be better optimized, and the flexibility and feasibility of the algorithm are improved.