The invention discloses a directional porous SiC and diamond reinforced Al base composite material and a preparation method thereof. The composite material is composed of a SiC ceramic phase, a diamond particle phase and a Al metal phase. The preparation method of the composite material comprises the following steps: 1, preparing directional porous SiC ceramic; 2, coating a WC coating layer on the surface of diamond particles; 3, filling directional porous apertures of the porous SiC ceramic with the diamond particles; and 4, allowing Al to spontaneously infiltrate into the directional apertures filled with the diamond particles. The directional porous SiC and diamond reinforced Al base composite material prepared through adopting the method has very high heat conductivity in a directional aperture direction, and can timely transmit heat generated by a semiconductor to heat sink in order to dissipate the heat; and the composite material has a heat expansion coefficient matched with a packaging substrate in a direction vertical to the directional aperture direction (the plane of a semiconductor device), so the heat stress between a packaging material and the semiconductor is reduced, the working efficiency of the semiconductor is improved, and the service life of the semiconductor is prolonged.