Junction is a necessary operation when vector-data entering into database to be stored. The current widespread use of junction is based on map. But the algorithm which restricted by the border of map canpsilat meet the demand of junction of arbitrary scope. In order to achieve the seamless integration of the spatial database after incremental updates, the algorithm of junction of arbitrary scope which has been made into large-scale GIS software MapGis7.3 is put forward. We find that the junction of massive spatial database is more efficient than traditional map junction, and the transition of vector-data after junction is smooth. Consequently, the effectiveness and accuracy of the algorithm are verified.