A polarization control plate (PCP) is applied to achieve incoherent superposition of beamlets on target for further improving illumination uniformity in inertial confinement fusion (ICF) driver. By analyzing the effect of PCP on the modification of the polarization of beamlets, the model for the transmittance function of PCP is built up. The effects of PCP on the characteristics on focal spot are simulated numerically and analyzed theoretically. The expectation and variance of degree of polarization (DOP) are used to describe depolarization characteristics on focal spot, and the contrast is employed to evaluate illumination uniformity. The effects of number of PCP elements, bandwidth and integral time on the characteristics on focal spot are discussed in detail. The results show that polarization control plate can well obtain depolarized laser beam and improve uniformity on target.