Abstract: It was proposed that all carbon clusters with n>30 have geometrically closed cage structures. The mass spectrum of C_(92-151)~+ was observed on a self-built laser probe time-of-flight mass spectrometer. The spectrum showed that for cluster size less or equal to 126, only even-number cluster exists, which is consistant with a closed structure. The system was broken for cluster larger than 126. This observation indicates that the structural configuration changes with increase of the cluster size.