An image noise intensity estimation method, an image noise intensity estimation device, and an image recognition device are disclosed. The method includes: obtaining a first image to be estimated; filtering the first image to obtain a second image; dividing the first and second images to obtain a plurality of first image sub-blocks and a plurality of second image sub-blocks respectively; calculating error values between the first image sub-blocks and the second image sub-blocks in corresponding positions; and estimating the noise intensity of the first image according to a plurality of error values obtained by calculation. The method can improve the accuracy of noise estimation.
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