Three wheat samples,Karl (American Hard Wheat with strong gluten),Jagger (American Hard Wheat with weak gluten) and Zimai 12 (Chinese Soft Wheat with weak gluten)and their defatted flours,obtained after lipids were extracted by chloroform,were used in this research to investigate the function of lipid on physicochemical properties and Mantou-making quality of wheat flour.Microstructure and thermal properties of these samples were measured by SEM and DSC respectively.The defatted flour had more single starch granules and higher gelatinization enthalpy than untreated samples.Rheologicai properties were determined by Farinograph,Rapid-Vasico Analyser and Mixolab.Contrasted with the untreated sample,defatted flour had a higher water absorption,longer pasting peak time,higher peak and hold viscosity,but lower setback and breakdown.Characteristics of the first two stage of Mixolab,dough development and protein reduction,didnt show evident difference except for water absorption.A distinct variation during the other three stages,starch gelatinization,amylasic activity and starch gelling were observed.It illustrated that defatted flour had a higher maximum consistency during starch gelatinization,a lower amylasic activity and a higher consistency value as dough temperature cooled down.The protein network of defatted samples denatured more rapidly.C-CELL technology and Textural Analyser were used to test internal grain and texture of Mantou.It showed that volume of Mantou made from defatted flour did not change obviously,but the crumb grain was poorer,showing bigger cell diameter,less cell number and thicker cell wall comparing to the untreated samples.These experiments demonstrated that lipid may play a more important role on starch-lipid matrix than protein-lipid matrix in dough and could influence Mantou-making quality of wheat flour.