The polarization control scheme is generally used for generating attosecond pulse, in which the high harmonic emission only occurs within a half optical period of polarization gating and thus the obtained harmonic spectrum is continuous in the whole plateau and at the cutoff position. Based on the Ammosov-Delone-Krainov tunneling ionization theory and the strong field approximation method, the effect of the intensity ratio of two-beam counter-rotating circularly polarized pulses in the polarization control scheme on atomic ionization probability and harmonic emission power spectra is investigated by numerical simulation. It is found that if the intensity ratio of two-beam pulses is properly controlled, the effective atomic ionization can take place in the first quarter of an optical period of polarization gating, which is beneficial to obtain an optimal high harmonic spectrum. Moreover, one can optimize the cutoff position and conversion efficiency of harmonic spectra according to the needs, provided the intensity ratio is always less than 1.