Abstract: An efficient image filter algorithm was proposed to filter the salt-and-pepper noise and keep the detail of gray scale image,simultaneously.At first,an improved and simplified PCNN model was used to locate the noisy pixel by a firing process without circulation.Then the graded median filter algorithm was proposed to filtering the noisy pixel while keep the non-noise pixel untouched.Computer simulations indicated the proposed method demonstrated the good filtering performance when filter different intensity of salt-and-pepper noise image and proved the validity of the algorithm by objective and subjective valuation.The proposed method showed better filtering results than existing methods when the noise intensity was high.