The invention provides an active capacitance pen and a posture detection method thereof, a capacitive touch screen and a touch system. The active capacitance pen comprises a first electrode, a second electrode, a third electrode and a control circuit for controlling communication between the first electrode, the second electrode and the third electrode and the capacitive touch screen; the control circuit simultaneously receives signals from the capacitive touch screen according to the first electrode and the second electrode to determine the inclination angle of the active capacitance pen, the first electrode and the third electrode are controlled by the control circuit to send signals to the capacitive touch screen separately, and the signals sent by the first electrode and the third electrode can be used by the capacitive touch screen for determining the azimuth angle of the active capacitance pen. Accordingly, the azimuth angle and the inclination angle of the active capacitance pen can be acquired, the structure and the circuit are simple, the positioning precision is high, and the posture detection university is improved.