OBJECTIVE： To establish the quality standard of ultramicro decoction piece of Meng medicine Gardenia jasminoides. METHODS： Microscopic identification character of the ultramicro decoction piece was observed； TLC was adopted for its qualitative identification； moisture， ash， extract were detected； HPLC was used for the content determination of geniposide： the column was Kromasil C18 with mobile phase of acetonitrile-water （15 ∶ 85，V/V） at a flow rate of 1.0 ml/min， detection wavelength was 238 nm， column temperature was 30 ℃， and injection volume was 10 μl. RESULTS： Cell wall was completely broken and the particle sizes were 5-60 μm. TLC spots were clear and well separated. The moisture was 3.89％-5.55％， ash was 3.13％-5.22％， acid-insoluble ash was 0.16％-0.80％， and extract was 29.2％-43.4％. The linear range of geniposide was 1.56-7.82 μg/ml （r＝0.999 9）； RSDs of precision， stability and reproducibility tests were lower than 2.0％； recovery was 100.17％-102.04％ （RSD＝1.07％，n＝6）. CONCLUSIONS： The standard can be used for the quality control of ultramicro decoction piece of Meng medicine G. jasminoides.