The invention discloses a method of measuring most-suitable lowest dissolved oxygen content required by fish. The fish of the same kind are evenly put in a water vat with the environment being suitable and the oxygen strength C0 being sufficient for feeding till being domesticated, the weight of each fish is weighed and the weight m0 of food eaten by the fish under the conditions the environment is suitable and the oxygen strength is sufficient is weighed, then the oxygen strength of the water vat is reduced to C1, and the weight of the food eaten when the oxygen strength is C1 is obtained; the previous steps are repeated till mx corresponding to the oxygen strength Cx is consistent with m0, and the most-suitable lowest dissolved oxygen content required by the fish is obtained. With the adoption of the method of measuring the most-suitable lowest dissolved oxygen content required by the fish, the most-suitable lowest dissolved oxygen content of various fish can be measured accurately, reference can be provided for oxygen charging of aquiculture, and the wasting of resources is reduced.