Objective To explore the compatibility rule of Huangqi [Radix Astragali

黄 芪] in Yifangkao（ Investigations of Medical Formulas

医方考）

thus providing the theoretical basis for the use of Huangqi in clinical practice. Methods Huangqi containing formulas were collected from Yifangkao

and then the functions of the Chinese herbs compatible with Huangqi were classified

and the frequencies of high-frequency herbs in each category were calculated. Results There were a total of 41 formulas with Huangqi

and the top five high-frequency categories of herbs are 1) tonics

2) exterior-releasing herbs

3) heat-clearing herbs

4) Qi-rectifying herbs

and 5) urinationpromoting and dampness-percolating herbs. The herb of highest-frequency with Huangqi is Gancao [Glycyrrhizae Radix Et Rhizoma

甘草]（ 28 times）

followed by Renshen [Ginseng Radix Et Rhizoma

人参]（ 27 times）

Danggui [Angelicae Sinensis Radix

当归]（ 25 times）

Baizhu [Atractylodis Macrocephalae Rhizoma

白术]（ 15 times）

etc. Meanwhile

different herbs are used with Huangqi when it plays different effects. Conclusion Huangqi are always used with tonics

exterior-releasing herbs

heat-clearing herbs

Qi-rectifying herbs as well as urinationpromoting and dampness-percolating herbs. When playing different effects

it should be combined with herbs with those specific characteristics.