Abstract: To design diamond bit matrix more scientific without the fluid medium under low temperature and low pressure,based on the high friction heat when diamond bits drill in the dry condition,a new method of adding graphite to the bit matrix is adopted to reduce the matrix's friction coefficient and friction heat.The effect of the content and the particle size of graphite on the matrix mechanical properties and friction performance under different environment is studied.The research results show that with increasing of the graphite content,the hardness,the bending strength and the friction coefficient of the matrix under normal temperature & pressure,and low temperature & pressure decrease gradually,while the abrasion loss decreases firstly,then increases,and from which the minimum abrasion loss is obtained when the graphite content reaches 7.5%.With the decreasing of the graphite particle size,the bending strength and the friction coefficient of the matrix decrease gradually,while the hardness and the abrasion loss of the matrix increases little by little.The feature analysis of the matrix after friction and wear also shows that to add proper graphite in the bit matrix can reduce its wear and help to lubricate the interface between the matrix and the drilled rock.