The invention discloses a guardrail lock sleeve, comprising a cross pipe, connection pipes, sleeve bodies and lock steel sheets, wherein four endpoints of the cross pipe are all fixedly connected with the connection pipes; one ends of the connection pipes are fixedly connected with the sleeve bodies; a lock groove is formed inside each sleeve body; a threaded hole runs through one side of the corresponding sleeve body; a lock nut is connected inside of the threaded hole in a threaded manner; one end of the lock nut is internally provided with a limit slot, and one end of the lock nut is run through by a limit rod; one end of a connection rod which runs through the lock nut is fixedly connected with a limit block; the lock steel sheets are arranged inside the lock grooves, and are connected with the lock nuts through the connection rods, so that the travelling nut may tighten and fix the guardrail, and assembly thereof is more convenient than a common lock sleeve; a rubber non-slip film is fixedly connected to one side of each lock steel sheet so as to prevent the guardrail from sliding to cause danger; moreover, by adopting a manner of the cross pipe, the guardrail can be constructed into a net shape, so that the security thereof is greatly increased, and the possibility of dangers when a child is playing is avoided.