The invention discloses a multifunctional warning type oil storage tank vacuum sealing device which comprises a sealing bottom cover, a micro vacuum pump, an oil level monitoring warning control system, a vacuum degree monitor and an air drier. The multifunctional warning type oil storage tank vacuum sealing device is simple and convenient to install and use, and various use performances of a simple horizontal type oil storage tank can be quickly improved only through simple installation on a manhole of the simple horizontal type oil storage tank. Therefore, the simple horizontal type oil storage tank has functions of micro vacuum negative pressure oil storage, vacuum linkage oil injection, air inlet automatic dehumidification drying, large opposite angle distance oil filtering, automatic real-time oil level monitoring warning and automatic shutdown after oil filling of an oil injection device. All-weather on-site oil treatment of insulating oil can be achieved, the on-site storage, oil filtering and oil level monitoring of the insulating oil are not subject to the influence of operation weather, environmental temperature and environmental humidity, the storage time of the insulating oil is effectively prolonged, and the on-site oil treatment working efficiency is improved.