An easy-installation full-size child window safety system for preventing children from leaning out and falling through open windows, comprising: - a flat form single cord connection profile with a single standard profile connection hole (2.1) to enable a single steel cord to be attached and two standard profile mounting holes to enable connection with the fixed window frame (x); - a flat form double cord connection profile (lb) with two standard profile connection holes (2.1) to enable two steel cords to be attached and two standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); and - a flat form multiple cord connection profile with multiple standard profile connection holes (2.1) to enable multiple steel cords to be attached and multiple standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); or comprising - a single cord stepped connection profile with a single standard profile connection hole (2.1) to enable a single steel cord to be attached and two standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); - a double cord stepped connection profile with two standard profile connection holes (2.1) to enable two steel cords to be attached and two standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); and - a multiple cord stepped connection profile (If) with multiple standard profile connection holes (2.1) to enable multiple steel cords to be attached and multiple standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); wherein - steel cord passes through the standard profile connection holes (2.1) on the single cord connection profile, the two cord connection profile and the multiple cord connection profile or passes through the single cord stepped connection profile, the double cord stepped connection profile and the multiple cord stepped connection profile (10, and which is prevented from releasing by a cord end clip and - a metal fastening part attached to the vertical and horizontal intersection points of steel cords used for fixing the cord or a plastic clamp part used for fixing the cord. - a flat form single cord connection profile with a single standard profile connection hole (2.1) to enable a single steel cord to be attached and two standard profile mounting holes to enable connection with the fixed window frame (x); - a flat form double cord connection profile (lb) with two standard profile connection holes (2.1) to enable two steel cords to be attached and two standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); and - a flat form multiple cord connection profile with multiple standard profile connection holes (2.1) to enable multiple steel cords to be attached and multiple standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); or comprising - a single cord stepped connection profile with a single standard profile connection hole (2.1) to enable a single steel cord to be attached and two standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); - a double cord stepped connection profile with two standard profile connection holes (2.1) to enable two steel cords to be attached and two standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); and - a multiple cord stepped connection profile (If) with multiple standard profile connection holes (2.1) to enable multiple steel cords to be attached and multiple standard profile mounting holes (2.2) to enable connection with the fixed window frame (x); wherein - steel cord passes through the standard profile connection holes (2.1) on the single cord connection profile, the two cord connection profile and the multiple cord connection profile or passes through the single cord stepped connection profile, the double cord stepped connection profile and the multiple cord stepped connection profile (10, and which is prevented from releasing by a cord end clip and - a metal fastening part attached to the vertical and horizontal intersection points of steel cords used for fixing the cord or a plastic clamp part used for fixing the cord.