Abstract: A 44 common-grid pixelated CdZnTe detector with different pixel sizes is designed and fabricated using the CdZnTe crystal. By the spectra measurement combined with weighting potential and electric field simulation, the small pixel effect and guide effect in common-grid pixelated CdZnTe detector are investigated. Results show that the spectroscopic characteristics of lager pixels are degraded since the small pixel effect is not strong enough to remove the hole trailing. While the spectroscopic characteristics of smaller pixels are also degraded since the serious charge loss in volume and surface layer between pixels and common-grid. An optimal energy resolution of 3.80% FWHM at 662 keV(137Cs radiation source) is obtained from the 0.8 mm wide pixel. Excessive high bias voltage increases the surface leakage current between pixels and common-grid, which in turn degrades the spectroscopic characteristics. The optimal bias voltage is -60 V for 0.8 mm wide pixel.