Abstract: The basalt fiber fabrics modified with self-made rare earth modifiers (La-BF) enhance the bisphenol-A dicyanate (BADCy). The influence of the modification on basalt fiber (BF) surface was analyzed by SEM and FTIR. The effect of the modification on the thermal stability of BF/BADCy composite was investigated by TG analysis. The modification of the BF/BADCy composites with different mass fractions were analyzed using an electronic universal testing machine. Influence of the flexural properties of the material, the influence of the modification on the dielectric properties of the BF/BADCy composites were analyzed by an impedance analyzer. The results show that the modification reduces the surface defects of the BF and introduces crystalline bulges, which is beneficial to improve the interface properties of the BF/BADCy composite. The modification increases the thermal decomposition temperature of the BF/BADCy composite, and the initial decomposition temperature is increased by 145℃. When the mass fraction of BF is 12wt%, the flexural modulus of the La-BF/BADCy composite is improved to 4.19 GPa and the flexural strength is over 110 MPa. In 1 MHz-3 GHz range, the dielectric constant of the La-BF/BADCy composite is around 1.9. Therefore, the rare earth modification can effectively improve the flexural properties, thermal stability and dielectric properties of BF/BADCy composites.