1. A computer implemented method for dialog management, comprising the steps of: S 1000 : receiving an utterance from a user by a terminal; S 2000 : recognizing and converting the utterance from sound into sequential words in a written text; S 3000 : determining if there is a phrase in the written text matching with a predefined phrase in a menu tree; wherein the menu tree comprises a root node, the root node comprises a plurality of parent nodes, and each parent node comprises at least one leaf node, each leaf node corresponds to an operation, each of the predefined phrases corresponds to a parent node or a leaf node; if the phrase in the written text matches with more than one of the predefined phrases in the menu tree, S 3110 : attempting to recognize at least one dynamic field in the written text; S 3120 : converting the sequential words into corresponding predefined terms in sequence, wherein different words with similar meaning are converted into a term; each of the predefined terms corresponds to a parent node or a leaf node; S 3130 : matching terms with the corresponding parent node or leaf node in a matched phrase node; S 4000 : conducting the operation according to the matched phrase node; if the phrase in the written text matches with exactly one of the predefined phrase in the menu tree, S 3210 : attempting to recognize at least one dynamic field in the written text; S 3220 : matching the phrases with the parent node or the leaf node, S 4000 : conducting the operation according to the matched phrase node; if the phrase in the written text does not matches with any of the predefined phrase in the menu tree, S 3310 : attempting to recognize at least one dynamic field in the written text; S 3320 : converting the sequential words into corresponding predefined terms in sequence, wherein different words indicating the similar intent are converted into a term; S 3330 : matching the terms with the corresponding parent node or leaf node in all nodes; S 4000 : conducting the operation according to the matched phrase node,