Described are a free space optical communications method, and a transmitter and a receiver. The method comprises: transmitting, by means of an optical signal, wireless data between a transmitter and a receiver; transmitting, between the transmitter and the receiver, a wireless detection signal different from the optical signal; detecting whether the wireless detection signal is blocked; and adjusting, according to a detection result, the transmission of the optical signal to reduce the intensity of the optical signal or suspend the transmission of the optical signal when the wireless detection signal is blocked.