Stilbenes, particularly resveratrol and resveratrol dimers, could effectively quench singlet oxygen (1O2). It was reported that both resorcinol and carbon-carbon double bond quenching 1O2 can participate in the mechanism. However, it is still not clear which structure plays a dominant role in quenching 1O2. To investigate the characteristic structure in the mechanism of quenching 1O2, the resveratrol, pterostilbene and piceatannol quenching 1O2 abilities were compared by UHPLC-QTOF-MS2 and UHPLC-QQQ-MS2. Results showed that catechol, carbon-carbon double bond and resorcinol participated in the quenching of 1O2. Catechol ring plays a leading role in the mechanism, and the contribution of the structures in quenching 1O2 activity are as follows: catechol ring > carbon-carbon double bond > resorcinol ring, which is supported by the calculation of energy. Our findings will contribute to the future screening of stilbenes with higher activity, and those stilbenes may have great therapeutic potential in 1O2-mediated diseases.