The invention provides a method for identifying key words in technical documents. The method for identifying the key words in the technical documents comprises identifying vocabularies with different length in the technical documents to form into a plurality of hash tables for the vocabularies with different length; ranking every hash table and extracting elements in the hash tables to form into a high frequency vocabulary list; removing incomplete vocabularies in the high frequency vocabulary list and obtaining a key word list. A system for performing the method for identifying the key words in the technical documents comprises a vocabulary processing device, a hash table processing device and an incomplete vocabulary removing device; the vocabulary processing device is used for identifying the vocabularies with different length in the technical documents to form into the plurality of hash tables for the vocabularies with different length; the hash table processing device is used for ranking every hash table and extracting the elements in the hash tables to form into a high frequency vocabulary list; the incomplete vocabulary removing device is used for removing the incomplete vocabularies in the high frequency vocabulary list and obtaining the key word list. The method and device for identifying the key words in the technical documents can assist an inspector to rapidly obtain key information in the technical documents.