An efficient optimization and design method has been proposed and developed for Enriched-gas Water-Alternating-Gas (EWAG) injection process. The proposed technique is able to quantitatively determine the sizes of the enriched-gas slug and water slug for each cycle of the water-alternating-gas (WAG) injection process, as well as the total number of injection cycles. Applying this method provides the opportunity to implement the WAG scenario more efficient and economical. The numerical simulation showed that in comparison with other conventional WAG scenarios with traditional optimization approach, the EWAG has the obvious advantages of evaluation of indices, such as the oil recovery factor and cumulative net cash flow.