The main colorant of Chelidonium majus extracts is a berberine which shows relatively good dyeability onto silk fabrics in the appropriate dyeing conditions without mordant, But cotton fabrics are difficult to dye with berberine because of the low substantivity the cationic to cellulosic fibers. we treated cotton fabrics using three types of polycarboxylic acid, DL-malic acid, citric acid, 1,2,3,4-butanetetracarboxylic acid(BTCA) to increase dyeability of Chelidonium majus extracts onto cotton fabrics. As a result the cotton fabrics treated with polycarboxylic acid could be dyed with Chelidonium majus extracts and also showed yellow vividly. The dye uptake were increased with increasing the number of carboxy groups. And so dye uptake resulted the largest in the BTCA solutions which have four carboxylic groups in the molecular unit. The optimal dyeing temperature a of Chelidonium majus extracts onto polycarboxylic acid treated cotton fabrics were $60^{circ}C$. The dye equilibrium was reached 20 minutes after dyeing. Neutral pH of dye solutions showed in higher K/S value than acidic or alkaline conditions. But the colorfastness to washing and light according to polycarboxylic acid treat was not enhance.