The invention discloses an extracting method and apparatus for a case auditing rule of a single disease, and a case auditing method and system for the single disease. The extracting method comprises the steps of performing word segment processing on each case of a training case set to obtain a plurality of segmented words, wherein the training case set comprises a plurality of cases belonging to preset single disease; establishing a word co-occurrence graph with multiple segmented words, wherein each segmented word is used as a top point of the word co-occurrence graph, and the weight of the side boundary between two top points is the co-occurrence time of the segmented word, corresponding to the two top points, in the training case set; obtaining key words from the multiple segmented words according to the word co-occurrence graph; forming a key word set according to the obtained key words; and extracting the case auditing rule specific to the single disease from the key word set, wherein the case auditing rule is a sequential key word sequence formed by the multiple key words from the key word set. Therefore, the case auditing rule for the single disease can be extracted for realizing the automatic auditing for cases of the single disease.