The invention discloses an intrinsically safe inerting protection method and an intrinsically safe inerting protection device for an oil storage tank, relates to a method and a device for active fire and explosion prevention of the oil storage tank, and aims to solve the problem of fire and explosion prevention of the oil storage tank. The method comprises the following steps: a, performing inerting on each oil tank in sequence to ensure that each oil tank achieves an inexplosive condition, namely, the oxygen concentration of gas in the tank is lower than 10 percent; b, detecting the pressure of a pipe network for supplying inert gas to the oil tank, and supplying the inert gas to the pipe network and inputting the inert gas to the oil tank through the pipe network if the pressure is lower than a set lower limit value; c, detecting the pressure of the pipe network for supplying the inert gas to the oil tank, emitting the inert gas in the pipe network if the pressure exceeds a set upper limit value; and d, detecting the oxygen concentration in the pipe network for supplying the inert gas to the oil tank, and repeating the step a if the concentration exceeds the set upper limit value. The device comprises a buffer device, a breathing pipe network, a first pressure transmitter, a second pressure transmitter, an online oxygen analyzer and an electric control device.