The invention provides a sprue bush demoulding and installing structure. The sprue bush demoulding and installing structure can simplify the installation of a sprue bush, and the installation can be implemented on the upper end surface of a sprue plate, so that the safety in the mould assembling process is improved. The sprue bush demoulding and installing structure comprises a sprue plate, a pad plate, a sprue bush, a plate A and a front mould, wherein a runner is formed inside the sprue bush; the runner penetrates through the plate A and the front mould; the upper part of the sprue bush is positioned inside an installing chamber of the sprue plate; a convergent structure at the lower part of the sprue bush is positioned inside a convergent installing chamber of the pad plate; the sprue bush demoulding and installing structure is characterized in that the pad plate is positioned inside a pad plate installing chamber of the plate A; the pad plate is supported on the front mould; an inclined guide slot which is inwardly convergent slantly from the top to the bottom is formed in each of the two sides of the pad plate; two inclined guide posts penetrate through the sprue plate and then are inserted into the corresponding inclined guide slots; cover plates are arranged on the upper parts of the inclined guide posts in a pressing manner; screws tightly fix the cover plates and the sprue plate from the top to the bottom.