There were 18 formulas that involved the combination of Radix Astragali seu Hedysari and Rhizoma Anemarrhenae in Records of Integrated Chinese and Western Medicine(Yixue Zhongzhong Canxi Lu)written by Zhang Xichun,which could treat seven kinds of internal medicine diseases. Radix Astragali seu Hedysari and Rhizoma Anemarrhenae,show the opposite drug nature and flavours. The former can tonify qi with effects of ascending and dispersing,while the latter can nourish yin with effects of descending and astringing. In Zhang’s 18 formulas that involved the combination of two drugs,when they were used in equivalent amount,it reflected the compatibility characteristics such as simultaneous supplementation of qi and blood,combination of tonifying and clearing methods for calming endogenous and exogenous wind,co-regulation of cold and warm for mutual restriction. When Radix Astragali seu Hedysari was more used with less Rhizoma Anemarrhenae,it mainly reflected the compatibility characteristics such as culturing primordial qi and ascending the sinking qi,preventing vanishing and relieving desertion,ascending the sinking qi and smoothing the secretion,making qi transformation orderly,combined application of drugs with sweet and bitter flavours,combination of tonifying and resolving methods. When Rhizoma Anemarrhenae was more used with less Radix Astragali seu Hedysari,it could simultaneously regulate the lung and spleen and nourish yin for astringing. Through the compatibility characteristics of 18 formulas,the unique opinions of Zhang’s academic thoughts and medication in syndrome differentiation and treatment were further understood.