Abstract: The composition of phosphate graphite casting mould is designed by using orthogonal test．The effect of each factor on the casting mould is analyzed,and a proper procedure to prepare phosphate graphite casting mould is determined in which phosphor,Al₂O₃ and graphite are mixed and modeled in the ratio of0．30：0．30：0．70and dried under the condition of 600℃ for about 40min．Test results show that the phosphate graphite casting mould exhibits better mechanical properties which the dry tensile strength and compressive strength arrive at 4．67×10⁵Pa and 22．21×10⁵Pa respectively．The optimum ratio range of Al₂O₃ powder over phosphor is 0．8～1．0．Relationship among σ_c,σ_t and influential factors respectively are： σ_c （10⁵Pa）＝0．71A（％）＋0．47B（％）＋0．022C（℃）－0．11D（min）－23．49, σ_t （10⁵Pa）＝0．165A（％）＋0．135B（％）＋0．0051C（℃）－0．0063D（min）－7．419． Phosphate graphite casting mould has better shock chilling capacity than sand mould．