M40J graphite fiber reinforced aluminum composite is fabricated by a vacuum liquid infiltration process and the effects of an acid phosphate binder on the properties of the fiber preform and its composite are studied in this paper. It is found that the atom ratio of Al/P in the acid phosphate, the content of the binder and the preheated temperature of the preform affect the compress property of the preform obviously. After adding 5% binder and heating it at 500℃, the preform has enough compress strength for liquid infiltration and the fiber distribute evenly in the composite. The tensile strength and the bend strength are greater than 500 MPa and 800 MPa respectively.