The present invention relates to a method of removing petroleum acid from hydrocarbon oil by a membrane dispersion extraction device. A continuous phase of the hydrocarbon oil is heated up to 10 DEG C to 150 DEG C; deacidification solvent dispersed phase is heated up to 10 DEG C to 90 DEG C; the cubage ratio of the continuous phase and the dispersed phase is 50 to 2 : 1; the pressure difference of the dispersed phase and the continuous phase is 0.05MPa to 0.4MPa; the flow velocity of the dispersed phase deacidification solvent is 0.5 to 5L/<2> per hour; membrane aperture is 0.01 to 60 microns; the dispersed phase deacidification solvent is dispersed into continuous phase oil through membrane micropores; clean oil after the deacidification is obtained after sedimentation and separation. The deacidification solvent is 1 percent to 15 percent of ammonia, 20 percent to 70 percent of alcohol or 0.02 percent to 5 percent of petroleum acid or 0.004 percent to 1 percent of demulsifier and thewater with the rest quantity. The contacting time of the oil and the solvent is short; mass transfer efficiency is high; the disposal capability is large; the extraction course is not emulsified easily; the hydrocarbon oil contains little alkali liquid; the device operation is convenient.