Abstract: In order to normalize the subject indexing of geosciences literatures gradually so as to meet the need for the retrieval of the literatures and realize automatic search by using the computer, the authors put forward some methods for solving the problems of subject indexing of the on-line index system of the Chinese geological literature database, emphasize the importance of correctly understanding the subject concept for subject indexing of the geological literature and elucidate the method of refining subject words and procedure of on-line indexing in this paper.