The invention discloses a rubbish mail filtering method based on partial matching forecast, comprising: 1) transform a novel mail into a character string composed of corresponding characters of 001-127ASC II; 2) extracting ancient rubbish mail training set, a normal mail training set, a rubbish mail forecast set and a normal mail forecast set; 3) training the normal mail training set and the rubbish mail training set into a rubbish mail model and a normal mail model through a partially matching forecast algorithm; 4) performing cross entropy operation on the character string and the rubbish mail model transformed by a novel mail with the normal mail, obtaining two cross entropy values; 5) determining whether the novel mail is the rubbish mail or the normal mail by the model with the smallest cross entropy; 6) after sorting the novel mail, adding the novel mail into the forecast set, performing incremental learning, obtaining a novel model. The invention effectively avoids the condition that the normal mail is used as the rubbish mail by mistake.