Interfacial interaction is an important factor determining the properties of polymer composites. Firstly, ultilized two-step reactions of silane coupling agent and maleic anhydride, the surface modification of layered aluminum phosphate (LAP) was prepared; then chain extended bismaleimide (BMI) resin prepolymer was obtained by 4, 4' -bismaleimide diphenylmethane (BDM) and 2, 2' -diallylbisphenol A (DABPA) reaction; finally, LAP/BMI composites was successfully prepared by mechanical blending and thermal curing. It was found that continuous, tight and low-defect interface binding was formed between modified LAP (m-LAP) particles and BMI matrix. Compared with pure BMI, the bending and tensile strength of m-LAP/BMI-3.5% composites at room temperature are 173.37 MPa and 86.79 MPa, which are increased by 15.14 % and 30.6 %, respectively. After heat treatment at 300 ℃ for 6 h, the bending strength of m-LAP/BMI-3.5 composites can still maintain 71.22 % of the normal temperature strength, which is much higher than that of pure BMI resin after heat treatment. The glass transition temperature (Tg) of m-LAP/BMI composites was increased to 234~240 ℃. The dielectric constant and dielectric loss of m-LAP/BMI-3.5 composite are 4.46 and 0.05 respectively. Therefore, the two-step surface modification can significantly improve the overall properties of LAP/BMI composites.