While inheriting family studies, Wan Mizhai pays attention to clinical practice, and has profound medical attainments, especially being good at feeling the pulse. Good at differential diagnosis of difficult diseases. In pediatrics, he summed up the three major causes of children on the basis of Thirteen Recipes of Heirloom, and put forward the view that prevention should be emphasized instead of over-medication. In gynecology, expounding the physiological and pathological characteristics of women and emphasizing the importance of nourishing qi and blood and regulating spleen and stomach have far-reaching influence in the history of gynecology of traditional Chinese medicine. The Shiwan Niuhuang Qingxin Pill invented by him is still a good medicine for treating acute convulsions in children. Wan Mizhai attached importance to the analysis of illness and used ancient prescriptions flexibly. Its prescription is less medicine, good curative effect, and it has created many miracles to bring back the dead, so it was called "imperial doctor" by people at that time.
Wan Mizhai spent decades summarizing and sorting out his ancestors' and his own medical theory and clinical practice experience, and wrote the Encyclopedia of Wan Mizhai Medicine, with a volume of 100, or about10.5000 words, which is another encyclopedia of traditional Chinese medicine in the history of China medicine after "A Thousand Daughters' Prescriptions". It brings together and develops the medical achievements of China16th century. It not only expounds the theory of traditional Chinese medicine and medical classics, but also discusses the prevention, health care, health preservation and prenatal education of diseases. The explanation is simple, the argument is incisive and the prescription is concise. Many chapters in the book are narrated in the form of poems and songs, which are well-known and have far-reaching influence on later generations and overseas.
Because of Wan Mizhai's noble medical ethics, superb medical skills, many contributions and great influence, he was buried in Guangjiagang, a big river bank in his hometown, in the form of "Imperial Funeral in Beijing" after his death. The villagers volunteered to build a shrine next to the grave as a memorial. Emperor Kangxi of Qing Dynasty named Wan Mizhai as a "medical saint".