This paper presents improved evolutionary operation based on D-optimal design and response surface method. D-optimal design and response surface method allow us to overcome the disadvantages of conventional evolutionary operation. Although evolutionary operation has been an effective alternative when fundamental models are hard to build because of the lack of the necessary information, the disadvantages in the number of experiments, experimental design and analysis and detection of the optimal point have prevented EVOP from being frequently applied to real processes. To compare the performance of the proposed method and the conventional EVOP, both of them were applied to a pulp digester process. As a result, the comparable response variable value has been clearly obtained with the proposed method while conducting much fewer numbers of experiments than the conventional evolutionary operation. In addition, the proposed method flexibly handles the constraints in the experimental design and gives more reliable experiment results than the conventional evolutionary operation. By virtue of these benefits, the proposed method can be utilized effectively for a process where prior knowledge for the process is not available.