The invention relates to a beam forming method and system. The method comprises the following steps: acquiring a three-dimensional position information of a communication terminal, computing a relative position between a base station and the communication terminal according to the 3D position information, and computing 3D angle information between this base station and the communication terminal according to the relative position; computing the downward inclination angle of this base station and the beam forming vector corresponding to the communication terminal according to the relative position and the 3D angle information; and performing beam forming on a transmitting signal according to the downward inclination angle and the beam forming vector.