An electrically desalting and decalcifying process for crude oil is disclosed. The method includes steps of feeding an aqueous solution of a decalcifying agent into a first-stage electrically desalting tank, performing first-stage decalcifying on the crude oil in the first-stage electrically desalting tank, feeding the decalcified crude oil into a second-stage electrically desalting tank and a third-stage electrically desalting tank, performing conventional electrically desalting treatment to obtain purified oil, maintaining the concentration of the decalcifying agent in the first-stage injected solution to be constant, returning first-stage decalcifying discharged water into the first-stage electrically desalting tank, cycling for a plurality of times of decalcifying, discharging all or a part of the first-stage decalcifying discharged water into a water treatment process system when the calcium ion concentration in the first-stage decalcifying discharged water is higher than 20000 [mu]g/g, recovering the decalcifying agent through processes of acidifying, solid liquid separation, extraction, rectification and stripping in the water treatment process system, and discharging waste water after treatment. The method is high in decalcifying efficiency. The waste water after treatment can be discharged directly. Influences on running of electrically desalting and decalcifying devices are less. Decalcification can be performed stably in an electrically desalting system in an oil refinery.