The relationship between the magnetic properties and the microstructure of Pt-Co permanent magnetic alloys was studied. X-ray diffraction （XRD） results indicated that the as-cast Pt-Co alloy has a texture microstructure. According to the scan electron spectrum （SEM） results, the as-cast alloy has a columnar structure and the columnar crystal grows along the cooling direction. After plastic deformation and recrystallization, the texture was disappeared and the grains became smaller and more uniform. Compared with the columnar structure of Pt-Co alloys, the magnetic properties of the recrystallized alloys were improved obviously. So the grain size and direction may be the main factors which can affect the coerivity of Pt-Co alloys.