Transmission control of the plasma on the metal surface in optical integration is very important. Structures are designed to couple the surface plasmon polaritons (SPPs) to the light wave in free space by surface wave holography. Interference light intensity is obtained through simulating the scalar superposition of the SPP wave beam and the target beam in free space. Groove structures are obtained by etching grooves at the maximum light intensity positions. When the SPP waves are incident to the designed structures, the grooves scatter the SPP waves into free space and then the waves superpose there, generating the required light beam. Based on the principle, two structures are designed for coupling the SPP waves to focus on one or two specified points in free space. The finite-difference time-domain method is used to verify the principle. This coupled manner can be used as a method for solving the detection problem in the surface plasmon integrated optics. The SPP signal is coupled into free space and detected by common photodetectors.