Early-Yuán literatus of Mángchéng 邙城 (Luòyáng region, Hénán). He wrote the principal doctrinal preface to 羅天益 Luó Qiānfǔ’s editio princeps of 李杲 Lǐ Dōngyuán’s KR3er120 Dōngyuán shìxiào fāng in Zhìyuán 3 / 1266. The preface gives the most substantial early commentary on the work’s pedagogical method, emphasising that Lǐ explicitly cautioned Luó against teaching formulae alone — students must master the materia medica first, and only afterwards study formula-composition. Yàn warns that the Shìxiào fāng should be read together with Lǐ’s doctrinal works (Yīxué fāmíng, Píwèi lùn, Nèiwài shāng biàn, Yàoxiàng lùn), not as a standalone formula-collection.