The characteristics of smoothing quasi-far-field speckles using a zero-correlati on phase plate are simulated numerically in general cases.A comparison between t he speckles with a zero-correlation phase plate and those with a random phase pl ate (in combination with a two-element polarization control plate) is given.The zero-correlation phase plates are designed for the perfect near-field irradiatio n and the far-field application.However,the results show that the quasi-far-fiel d speckle intensity modulations using a zero-correlation phase plate are much sm aller than those with a random phase plate under the case of defocus distance le ss than 0.002355λf2/d2 and the incident field with random variations of amplitude (≤10%) and phase (≤λ/20).Therefore,the zero-correlat ion phase plates can still smooth quasi-far-field speckles effectively.