Abstract: Six- and ten-state close-coupling calculations are carried out by using the R-matrix method to obtain photoionization cross section of the ground state of C II ion. The incident photon energy ranges from 1.8Ry to 4.3Ry. The calculated results in Length and Velocity formulations agree very well. The cross sections contain complicated resonance structure. Our results are also in good agreement with those of the Opacity Project. The difference between the six-and ten-state close-coupling calculations shows that the resonance series converging to higher ionization thresholds will disturb the lower Rydberg resonances. The energy levels of singly and doubly excited states can be determined by the resonance structures of partial and individual cross sections.