A window frame assembly has a built-in foldable screen, having a body, the body having at least a first frame part and a second frame part; the first frame part has at least a first end surface and a second end surface; the second end surface is fixedly connected to the second frame part; the first end surface is provided with a protruded guiding convex part; the guiding convex part is provided with a line receiving groove; and two sides of the line receiving groove are respectively provided with a concave part. The above structure has the benefits of enabling the guiding convex part located on the transverse frame in the foldable screen module to be re-assembled on the structure of the window frame assembly, thus reducing the number of foldable screen module components, and also improving the convenience of assembling the foldable screen module in the window.