Abstract: The paper aims to study physiological changes during leaf color change in Pyrus calleryana Decne, and found the relationship between leaf color and physiological changes and the mechanism of color change. Determined by UV spectrophotometer and portable chromatic meter, soluble sugar, anthocyanin, chlorophyll and carotenoid content, leaf color parameters of lightness △L and hue parameters △a and △b were tested in Pyrus calleryana Decne during leaf color change. Anthocyanin generally rose during leaf color change, while chlorophyll and carotenoid content gradually reduced; the soluble sugar content was higher and stable. Chlorophyll was correlated with anthocyanin contents. There was significantly negative correlation between carotenoid and anthocyanin contents in the leaves of‘Capital’and‘Red Spire’, while‘Aristocrat’and‘New Bradford’were not significantly correlated. Soluble sugar contents of four varieties were not correlated with anthocyanin. The correlation between △a values and anthocyanin contents was significantly positive, but △a values had a significantly negative correlation with chlorophyll. There was significantly negative correlation between △a values and carotenoid in‘Capital’and‘Red Spire’. △L value of‘Capital’was significantly and negatively correlated to anthocyanin, but △L values of others were irrelevant with chlorophyll and anthocyanin. The △b values were not significantly correlated with chlorophyll, carotenoid and anthocyanidin contents. The leaf color of Pyrus calleryana Decne was mostly affected by chlorophyll and anthocyanin, carotenoid was not the main pigment, soluble sugar was good for leaf color maintenance.