Window casing with high-density fiber cement board

The utility model discloses a window casing with a high-density fiber cement board, which relates to the technical field of buildings and comprises the high-density fiber cement board, a steel keel, an ALC (autoclaved lightweight concrete) board, a first auxiliary frame, a second auxiliary frame and an aluminum window frame, and the first auxiliary frame is provided with a first border and a second border; the second auxiliary frame is connected with the high-density fiber cement board and corresponds to the aluminum window frame; the upper side of the high-density fiber cement board is provided with a drainage groove convenient for discharging supplied water, and the lower side of the high-density fiber cement board is provided with a guide groove used for guiding out the water; sealant is arranged on the high-density fiber cement board; by adopting the high-density fiber cement board, the steel keel and the ALC board, the stability and the sealing effect of the whole structure are improved, and the waterpro