The embodiment of the invention discloses a method and a device for calculating similarity between strings. The method comprises the steps that the weight of core vocabularies of at least two strings is acquired; a maximum common sequence of the strings is acquired, and the weight of the maximum common sequence is determined according to the length and vocabularies of the maximum common sequence; the weight of common vocabularies in the strings is acquired according to a preset weight table of the common vocabularies; the similarity between the strings is acquired according to the weight of the core vocabularies, the weight of the maximum common sequence and the weight of the common vocabularies. According to the method, sentence structure analysis is added, and vocabulary weight information is also added to serve as a harmonic value for string similarity calculation; due to the accuracy of a word segmentation tool, some errors will be generated in the word segmentation result, sentence structure analysis will also has a certain error, and the calculation result is more accurate after word frequency weight harmonizing.