We study the phase transition properties of the two-dimentional q-state clock model by an extensive Monte Carlo simulation. Several independent physical quantities, including the specific heat, the magnetization and the helicity modulus had been calculated for q > 5. The specific heat and the magnetization shows the behavior of two distinct phase transitions, including the higher phase transition, T2, between the disordered phase and the quasi-long-range ordered phase and the lower phase transition, T1, between the quasi-long-range ordered phase and the quasi-long-range ordered phase. The helicity modulus not only show that T2 is the Kosterlitz-Thouless phase transition but also has signature of phase transition around T1.