The invention discloses a high precision separation method for light beams with same signal light receiving and transmitting frequency in spatial laser communication. Aiming at the scheme that a current laser terminal adopts a same frequency band and different frequency points for receiving and transmitting, the first problem to be solved is polarized separation of receiving and transmitting light beams, so that feasibility of achieving the scheme of the same frequency for receiving and transmitting in engineering depends on whether polarized isolation of the system can meet a requirement; therefore, the method provided by the invention adopts a rotary optical wave plate to achieve interchanging of polarization states of the receiving and transmitting light beams, and thus transmits left-handed light/right-handed light and receives the right-handed light/ left-handed light; meanwhile, in combination with a novel polarizing beam splitter structure design, the method achieves high precision light transmission isolation, and thus transmitting power can reach a watt (W) level, sensitivity of a receiving end can reach a nanowatt (nw) level, and receiving and transmitting isolation is superior to 60db.