The invention relates to a touch-sensitive display device and a method judging a touch-sensitive mode. The touch-sensitive display device comprises a control module, a resistor touch-sensitive panel and a measuring unit. The resistor touch-sensitive panel comprises a first conducting layer and a second conducting layer. The method comprises the following steps: the first conducting layer contactswith the second conducting layer; the voltage value of the second conducting layer is measured so as to obtain a first voltage and a second voltage; of the difference of the first voltage and the second voltage is less than the preset error value, a touch-sensitive pen operating mode is started; and if the difference of the first voltage and the second voltage is more than the preset error value,a finger operating mode is started. The touch-sensitive display device can immediately convert into the touch-sensitive pen operating mode or the finger operating mode so as to achieve different operating effects when the user touches by a touch-sensitive pen or the finger.