For lack of written records, we do not now know how Hai Ying came to master the diagnostic skills of Chinese medicine and to learn to mix and prepare drugs. Some say that he had already studied the practice of medicine back home in China, while others maintain that he learned his craft from an old Chinese doctor in America.
由於缺乏文字資料，後人對海應如何學習中醫望、聞、問、切的把脈本領，和調劑、煎藥的過程並不清楚，有人說他在家鄉已學習醫術，另有一說則指他是跟隨當地的老中醫學習。