This study is aimed to identify the process characterization of the cell culture of the biopharmaceutical erythropoietin alpha. In biopharmaceutical manufacturing, ensuring safety and efficacy should always be target qualities. The “quality by design” initiative provides guidance on pharmaceutical development to facilitate design of products and processes that maximizes the product′s efficacy and safety profile while enhancing product manufacturability. Fundamental to this approach is an understanding of the relationship between the quality attributes of the product and their impact on safety and efficacy. The DoE approach focuses on quality‐by‐design (QbD). To implement QbD, we report on a case regarding the production of erythropoietin alpha using cultured Chinese hamster ovary cells. Changes in the four critical process parameters (CPPs) of RPM, pH, dissolved oxygen, and temperature were evaluated. To evaluate the DoE, the three CQAs of Z‐value (N‐glycan score), host cell protein content, and erythropoietin alpha concentration (titer) were monitored and analyzed. Multivariate regression analysis between CPPs and CQAs were used to identify the design space needed to satisfy the targeted CQAs. We used QbD techniques and found optimal conditions for the cell culture process of erythropoietin alpha. Monte Carlo simulation was used under the optimized conditions and the set points were verified. As a result, it was confirmed that the optimal operational range was RPM 191.1–209.0, bioreactor temperature 32–34 °C, pH 7.0–7.2, and dissolved oxygen 24.9–35.1. This scientific understanding facilitates establishment of an expanded design space. In these situations, opportunities exist to develop more flexible regulatory approaches.