Abstract: In order to investigate the mechanism that slow cooling inhibits the browning of Yali pears after harvest, the effect of different cooling methods on membrane fatty acid components, contents, phase transition temperature, lipoxygenase (LOX) activity and browning of core of Yali pears with different harvest period were studied. The results showed that fatty acid components of core contained lauric acid, tetradecanoic acid, palmitic acid, palmitoleic acid, perlatolic acid, stearic acid, oleic acid, linoleic acid, linolenic acid. And the contents of linoleic acid, palmitic acid and oleic acid were more. Slow cooling increased linolenic acid and linoleic acid relative contents and unsaturated-saturated fatty acid ratio (U/S) value, reduced the phase transition temperature, significantly inhibited LOX activity and browning of the core of early harvested Yali pears. Late harvest increased the U/S value, reduced the phase transition temperature of the core. But because the harvest period was later, fruits senesced more quickly, LOX activity rose quickly in the late period, and membrane lipid peroxidation got serious. All these changes mentioned above finally made the late harvested fruits much easier to get browning. In a word, early harvesting and slow cooling could increase the contents of unsaturated fatty acid and U/S value, restrain the core browning of Yali pear after harvest.