stable geometrical configurations of electronic states for C42+ are found with QCISD/6-311G method. These configurations are Cs,C∞v,C2v,D2h,D∞h,D4h,D2d and C3v, etc. The Jahn-Teller distortions from the configurations C42+(Td) and C42+(D4h) exist. The analysis of the relationships among these various geometrical configurations, based on the Jahn-Teller effect, vibronic interaction and the resolution of group representations, is in agreement with the calculated results. The most stable electronic state of C42+ is 3A″ of the planar Cs configuration.