The invention discloses a pressure adjustable type plunger gas-lift wellhead device and a monitoring method thereof. The pressure adjustable type plunger gas-lift wellhead device comprises a remote operating platform, a blowout prevention pipe and a bypass pressure adjusting pipeline; a side opening of the blowout prevention pipe is connected with the bypass pressure adjusting pipeline, and the bypass pressure adjusting pipeline is internally provided with a 90-degree pressure-bearing ball-shaped adjusting valve; and the remote operating platform is connected with the 90-degree pressure-bearing ball-shaped adjusting valve and is used for sending a signal to the 90-degree pressure-bearing ball-shaped adjusting valve to control opening and closing of a wellhead. The pressure adjustable typeplunger gas-lift wellhead device has the characteristics of simple structure and convenient operation, product development and on-site use of the pressure adjustable type plunger gas-lift wellhead device can greatly reduce the workload of on-site staffs, automatic and intelligent management of fluid discharging of a plunger in a gas field are strengthened, and the difficult problem of plunger welloperation is solved.