Objective: To determine the monosaccharide compositions and their contents in polysaccharides from Pinus yunnanensis cone. Method: Trifluoroacetic acid was used to hydrolyze polysaccharide from P. yunnanensis cone and PMP derivatization was used to hydrolyze monosaccharide products. The monosaccharide compositions in polysaccharide from P. yunnanensis cone were determined by HPLC. Orthogonal test was conducted to investigate the hydrolyzing conditionsdesign;changes in size of the peak area of monosaccharide derivants derived from different reaction time and the amount of NaOH were compared to determine the optimum hydrolysis condition and the best derivatization condition. Result: The polysaccharides from P. yunnanensis cone were composed of mannose(Man)

rhamnose(Rham)

glucuronic acid(GlcUA)

galacturonic acid(GalUA)

glucose(Glc) and galactose(Gal)

xylose(Xyl)

arabian sugar(Arab)

and fucose(Fuc)

with content ratios of 1.10:0.04:0.63:0.14:1.00:1.11:1.80:0.60:0.09.The optimal hydrolysis condition:concentration of TFA 1 mol·L-1

hydrolysis temperature 100℃

hydrolysis time 6 h. The optimal derivatization condition:add 0.3 mol·L-1 NaOH in derivatization process

with a derivatization period of 40 min. Conclusion: The method is quick

simple with high sensitivity. It is a reliable method for the determination of the monosaccharide compositions in polysaccharides from P. yunnanensis.