The invention discloses a resistivity measuring method, device and system. The method comprises the following steps of: placing a core to be tested after being treated with 100% saturated water into acore holder, and injecting a predetermined confining pressure through a confining pressure pump; opening a displacement source for displacement, obtaining a current value through a current meter by apredetermined time interval, and obtaining a voltage value by a voltmeter; and determining the electrical resistivity of the core according to the current value, the voltage value, the arc length ofa curved electrode, the radius and length of the core. The method can realize the determination of the rock resistivity in the vertical direction under the formation condition for the plunger type core without changing the technique and the way of making the core.