The invention relates to a right-angle screwing connection structure of a plastic steel window frame and an installing method of the right-angle screwing connection structure. The right-angle screwing connection structure comprises a first plastic steel sectional material, a second plastic steel sectional material and a connecting element, wherein the first plastic steel sectional material and the second plastic steel sectional material are mutually vertical, the connecting element comprises an outer sheathing element, an inner embedding element and a steel inserting element, and the first plastic steel sectional material and the second plastic steel sectional material are fixedly and vertically connected into a whole through the connecting element. The right-angle screwing connection structure of the plastic steel window frame has the advantages that the connecting element is adopted at a connecting part of the window frame for realizing the combination and connection, the traditional welding mode is completely replaced, on one hand, the occurrence of aggregation is eliminated, the appearance effect of the plastic steel window frame is beautified, on the other hand, the plastic steel window frame can be combined and dismounted, in a special application scene, the plastic steel window frame can be dismounted for replacing the occupied physical space, and the transportation, the loading and the unloading are convenient. Meanwhile, the right-angle screwing connection structure of the plastic steel window frame has the advantages that the installation is convenient, the processing process is simple, the manufacturing and production cost is low, the effect is good, obvious social benefits and economic benefits are realized, and the right-angle screwing connection structure of the plastic steel window frame is worth of being popularized and applied.