The time of flight mass spectrometric technique was used to determine the initial mean kinetic energy of small fragment ions C+n (n≤11) produced from C60 excited by 532nm nanosecond laser pulses. The measured kinetic energy shows little variation with the fragment mass and the laser fluence in a broad range. Based on the assumption that C+30 is produced predominantly by a single electron emission followed by successive C2 evaporation from hot C60 in the nanosecond laser field，the formation of small fragments is interpreted as the complete breakup of the unstable C+30 cage structure. The interpretation is consistent with the previously observed results.