The　interaction　between　two　similar　plane　double-layers　for　Al2(SO4)3　type　asymmetric　electrolytes　was　investigated　with　the　aid　of　parameter　method.　The　interaction　energies　for　the　system　at　positive　surface　potential　were　expanded　in　the　power　series　at　low　and　high　potential,　respectively.　The　high　potential　formula　can　be　applied　to　0.2yey020.　This　almost　covers　with　the　bounds　of　all　potential,　and　that　the　calculative　method　is　relative　simple.　The　accurate　numeral　results　and　V＇-d　curves　were　given　for　y020.　When　y05,　V＇　hardly　change　with　y0.　The　interaction　energies　between　two　similar　plane　parallel　double　layers　for　the　different　type　electrolytes　at　y0=1　were　compared.　The　present　results　are　also　fit　for　Mg3(PO4)2　type　electrolytes　at　negative　surface　potential.