The invention discloses a method and a device for recognizing a character string in an image, which belong to the technical field of computers. The method comprises steps: according to image data of a character string-included sample image block stored in a training sample library and based on a convolutional neural network algorithm, an expression for a possibility set corresponding to a character string recognition result of the sample image block is built, wherein the expression for the possibility set is formed by to-be-determined parameters; based on a principle that the character string recognition result determined according to the possibility set is that the possibility of the character string included in the pre-stored sample image block is the maximum, the to-be-determined parameters are trained, and training values of the to-be-determined parameters are obtained; and when a to-be-recognized target image block is acquired, based on the convolutional neural network algorithm and the training values of the to-be-determined parameters, a target possibility set corresponding to the character string recognition result of the target image block is determined, and according to the target possibility set, the character string recognition result of the target image block is determined. Thus, the recognition accuracy can be improved.