Disclosed are a secure communication method and system. In a wireless communication environment in which there is a wiretapper wiretapping a signal transmitted by a first transmitter to a first receiver, the secure communication method calculates a beamforming vector including first and second beamforming vectors based on channel information between the second transmitter and the first receiver and channel information between the second transmitter and a second receiver, and performs beamforming on the first and second receivers with the calculated beamforming vector. Accordingly, even when it is unable to know channel information of a wiretapper, the secure communication method can satisfy the minimum service-quality requirements of a secondary user and maximize a primary user's secure ability.