The preparation process and properties of hexagonal boron nitride（h-BN）particle reinforced magnesium matrix composites were investigated.A thin layer of pure nickel was coated on the surface of h-BN particles by electroless plating

which can significantly improve the wettability between h-BN and magnesium alloy melt and strengthen the interface bonding with the matrix.By adding Y element to magnesium alloy and consume Ni element fused with the nickel-plating layer

the long period stacking ordered（LPSO）structure composed of Mg-NiY can be successfully formed

and the magnesium matrix composite reinforced by hybrid h-BN and LPSO structure is obtained.After ultrasonic treatment（UT）

the thermal conductivity（TC）of the magnesium composite containing 3% h-BN reaches 99.92 W/（m·℃）

and the average coefficient of thermal expansion（CTE）of the composite from room temperature（RT）to 100℃is 18.36×10

-6

K

-1

.The tensile strength and elongation of the composites reach 171 MPa and 3.9%

respectively.The magnesium alloy material with both high mechanical properties and excellent thermal properties was obtained.