In 1913, he began to translate the I Ching under the tutelage of the scholar Lao Naixuan. He finished the project ten years later in Beijing, and then the year after that he returned to Frankfurt, Germany to become one of Europe's preeminent sinologists.
他從 1913 年春天開始動手翻譯《易經》，在國學大師勞乃宣指導下，前後長達 10 年，1923 年終於完成於北京。次年衛禮賢返回德國法蘭克福，成為享譽歐洲的漢學家。