Community analysis is an important way to ascertain whether or not a complex system consists of sub-structures with different properties. In this paper, we give a two level community structure analysis for the SSCI journal system by most similar co-citation pattern. Five different strategies for the selection of most similar node (journal) pairs are introduced. The efficiency is checked by the normalized mutual information technique. Statistical properties and comparisons of the community results show that both of the two level detection could give instructional information for the community structure of complex systems. Further comparisons of the five strategies indicates that, the most efficient strategy is to assign nodes with maximum similarity into the same community whether the similarity information is complete or not, while random selection generates small world local community with no inside order. These results give valuable indication for efficient community detection by most similar node pairs.