The invention relates to an electric quantity balance control method for a tandem power battery pack. The method comprises the following steps: (S1) calculating each monomer remaining capacity according to monomer volume and monomer battery charging state SOC in the tandem power battery pack, and sorting the monomer remaining capacities from small to large; (S2) calculating monomer remaining capacity standard difference a in the tandem power battery pack; (S3) if the monomer remaining capacity standard difference a is larger than a dispersion set value b, entering a step (S4), and otherwise, carrying out electric quantity balance operation; and (S4) balancing each monomer remaining capacity according to a maximum value-minimum value pairing balance rule and a secondary maximum value-secondary minimum value pairing balance rule of the remaining capacity. Compared with an existing electric quantity balance control method for the tandem power battery pack, the method disclosed by the invention has the advantages that the complete charging and discharging of the tandem power battery pack can be realized, the utilization efficiency of the energy of the tandem power battery pack is improved, and the service life of the tandem power battery pack is prolonged.