The utility model relates to a side opening window type gate blowout preventer which is characterized in that an oil cylinder, a piston, a piston rod, a cylinder cover and a locking device assembly are fixed at both ends of a shell body, the side wall of the shell body is provided with one or two windows, side covers are fixed on the windows, the periphery of the side cover is provided with bolt holes and the side covers are fixed on the windows of the side wall of the shell body by bolts. When a gate is maintained, the side covers of the windows are opened to take out a gate assembly to carry out maintenance. The oil cylinder, the piston, the piston rod, the cylinder cover, the locking device assembly, etc. are not influenced when the gate is maintained. The utility model provides convenience for the maintenance and the exchange of the gate or a rubber core. The utility model reduces the chance that a side gate is opened and keeps the very good sealing performance of the blowout preventer.