Using basalt fiber-reinforced polymer （BFRP） bars to replace traditional steel bars and developing BFRP bar-reinforced seawater and sea sand concrete structures provided a new solution to simultaneously address the shortage of river sand resources and the easy corrosion of steel bars in marine concrete structures. However， BFRP bars might still suffer from fiber-resin interfacial bonding degradation and resin matrix hydrolysis in highly alkaline environments，which further leads to the degradation of their mechanical properties.Based on the electromechanical impedance （EMI） technique，a piezoelectric patch-BFRP bar degradation monitoring sensor was developed.Combined with accelerated corrosion tests，the degradation process of the interlaminar shear strength of BFRP bars and the variation law of the sensor monitoring signals were measured and analyzed.The results show that under high temperature and strong alkaline environments，with the increase of corrosion age，the interlaminar shear strength of BFRP bars first increases slightly and then decreases continuously.In contrast，the characteristic peak frequency and various statistical damage indices of the sensor conductance response exhibit regular monotonic increasing or decreasing changes.By establishing regression equations between the sensor characteristic indices and the mechanical property indices of BFRP bars，the quantitative prediction of the degradation degree of BFRP bars is realized.