A low profile linear reflective polarization conversion surface in the Ku band (12-18 GHz) is proposed using a metasurface, which can convert a linearly polarized incident wave into its orthogonal polarization states in the Ku band. The principle of designing such a polarization conversion surface is given. The physical working mechanism of a polarization conversion surface is clarified. The simulation is used to determine the positions of resonance points of the polarization conversion surface. The test results show that the proposed polarization conversion surface has a conversion efficiency of more than 80% within the working band, and has the advantages of high conversion efficiency, small size, small thickness, and simple structure.