The invention discloses a three-proofing window with high safety. The three-proofing window comprises a window frame, a screen window and a window sash, wherein a first step frame, a second step frame and a third step frame are sequentially arranged on the front side of the window frame from inside to outside, a square-frame-shaped fixing groove is further formed in the portion, on the inner side of the first step frame, of the window frame, the rear side wall of the screen window is provided with a first square-frame-shaped boss matched with the square-frame-shaped fixing groove, the first square-frame-shaped boss is embedded in the square-frame-shaped fixing groove so that the screen window and the window frame can be fixedly connected together, the front side wall of the screen window is provided with a screen fixing mechanism, a second square-frame-shaped boss matched with the second step frame is arranged on the rear side wall of the window sash, the window sash is installed in the third step frame through a hinge, and the second square-frame-shaped boss is arranged in the second step frame. According to the three-proofing window, the installation strength of the screen window can be improved, the edge of the screen window is prevented from being pulled out by external force, and the safety of the three-proofing window is effectively improved.