A method for compensating data voltage in a display device comprising a plurality of pixel units connected to a data line, each pixel unit comprising a thin film transistor, the method comprising the steps of: determining whether a current frame is identical to a previous one frame; not compensating the data voltage if the current frame is not identical to the previous frame; outputting a compensation data voltage to compensate data voltage of the current frame if the current frame is identical to that previous one frame, the step of outputting compensation data voltages to compensate data voltages in the current frame further comprising steps of: calculating a difference value of a maximal gray level and a minimal gray level of all the pixel units connected to the same data line; judging whether the difference value is larger than a critical value; if the difference value is smaller than or equal to a critical value, not compensating the data voltage; if the difference value is larger than the critical value, outputting data compensation voltages corresponding to all the pixel units connected to the data line to compensate the data voltages of all the pixels connected to the data line so that an influence of a leakage current of the thin film transistor on the pixel voltage at other pixel electrodes on the data line is reduced and a vertical crosstalk phenomenon is improved; and outputting information about the frame according to the compensated data voltage. determining whether a current frame is identical to a previous one frame; not compensating the data voltage if the current frame is not identical to the previous frame; outputting a compensation data voltage to compensate data voltage of the current frame if the current frame is identical to that previous one frame, the step of outputting compensation data voltages to compensate data voltages in the current frame further comprising steps of: calculating a difference value of a maximal gray level and a minimal gray level of all the pixel units connected to the same data line; judging whether the difference value is larger than a critical value; if the difference value is smaller than or equal to a critical value, not compensating the data voltage; if the difference value is larger than the critical value, outputting data compensation voltages corresponding to all the pixel units connected to the data line to compensate the data voltages of all the pixels connected to the data line so that an influence of a leakage current of the thin film transistor on the pixel voltage at other pixel electrodes on the data line is reduced and a vertical crosstalk phenomenon is improved; and outputting information about the frame according to the compensated data voltage. calculating a difference value of a maximal gray level and a minimal gray level of all the pixel units connected to the same data line; judging whether the difference value is larger than a critical value; if the difference value is smaller than or equal to a critical value, not compensating the data voltage; if the difference value is larger than the critical value, outputting data compensation voltages corresponding to all the pixel units connected to the data line to compensate the data voltages of all the pixels connected to the data line so that an influence of a leakage current of the thin film transistor on the pixel voltage at other pixel electrodes on the data line is reduced and a vertical crosstalk phenomenon is improved; and outputting information about the frame according to the compensated data voltage.