A detachable gas injector adaptable to semiconductor equipment includes a top cover, a hollow sleeve, a top housing and a gas output unit. The hollow sleeve receives a convex part of the top cover, thus forming a first transmission passage between the hollow sleeve and the convex part. The top housing has a center hole for accommodating the hollow sleeve, thus forming a second transmission passage between the hollow sleeve and the center hole. The gas output unit is connected to a bottom surface of the hollow sleeve. The gas output unit includes a first partition plate and a second partition plate, which form a first gas output layer, a second gas output layer and a third gas output layer.