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We report a measurement of the photoionization cross-section of the lithium 2P3/2 state in a magneto-optical trap (MOT) by means of a single-frequency cw laser. Intensity of the photoionizing radiation seen by atoms is determined by means of averaging the intensity distribution of the photoionizing beam over the spatial distribution of trapped atoms. We use the photoionizing laser beam with large waist to reduce a possible misalignment between the photoionizing beam and the MOT density distribution. The excited state fraction is also accurately measured under our MOT conditions. The near-threshold photoionization cross-section of lithium-7 2P3/2 state at λPI = 349.846(1) nm is found to be equal to σ = 13.7(1.4) Mb, with better accuracy in comparison with the previous measurements. We study the variation of the photoionization cross section on the polarization of the ionizing beam. Further experiments are suggested. [ABSTRACT FROM AUTHOR]