An Active-Matrix Organic Light Emitting Diode (AMOLED) display apparatus and a brightness compensation method thereof are provided. At an initial compensation stage, a display screen can be subjected to brightness calibration by an image sensor so as to acquire a data voltage compensation value of each sub-pixel when a brightness value of a display panel equals a preset value, a first data voltage is output to a corresponding pixel circuit according to the data voltage compensation value of each sub-pixel, a sensed voltage of each sub-pixel at this stage is used as an initial reference voltage of each sub-pixel when the brightness value of the display panel equals the preset value; and at a subsequent compensation stage, by regulating a data voltage of each sub-pixel, the sensed voltage of each sub-pixel is made to be equal to the corresponding initial reference voltage when the brightness value of the display panel equals the preset value, so as to achieve uniform compensation on brightness of each sub-pixel at the subsequent compensation stage. Thus, not only are uniformity and accuracy of initial brightness compensation improved, but also pixel aging is accurately compensated and uniformity and accuracy of subsequent compensation are improved.