The present invention discloses a single microphone hearing aid noise reduction method. The method comprises: acquiring an original sound signal, identifying the noise characteristics of noise in the original sound signal; iteratively training the noise reduction formula obtained by noise identification, optimizing the noise reduction formula, and acquiring the optimal values of parameters in the noise reduction formula; calculating the original sound signal according to the noise reduction formula optimized by iterative training and the specific value of each parameter, and outputting the signal to noise ratio of the noise; and judging whether the signal to noise ratio is qualified, and if qualified, carrying out hearing aid processing of the processed sound signal. The present invention can quickly identify, suppress and converge unsteady noise by single microphone noise reduction without the aid of special iterative adaptive learning filter hardware built in a hearing aid chip.