The properties of equal-higher-power difference squeezing of multimode entangled state light - field composed of multimode complex conjugate coherent state, multimode complex conjugate imaginary coherent state and multimode vacuum state are studied by utilizing the multimode squeezing theory in decoherence. The results show that when some fixed conditions are satisfied the mixed entangled state light - field mentioned above not only has the equal - higher - power difference squeezing in one of the two quadratures but also displays the similar effects in the two quadratures simultaneously, that is called "two - sided difference squeezing". This is a newly physical phenomenon which contradicts the principle of uncertainty.