Co-deposition of silicon carbide particles and carbon (or carbon sources) particles is essential for preparation of reaction bonded silicon carbide (RBSC) products by slip casting. The way of co-depositing of silicon carbide particles and carbon particles during slip casting process, and the influence of composition of raw particles on particle co-depositing in green bodies were studied. The experiment results show: 1.Co-deposition of binary particles is greatly affected by particle size distribution, and large proportion of rigid SiC particles increases the difficulty in demoulding procedure because of small shrinkage; 2. Dispersants in deposited cake trend to enrich at the surface in contact with mould wall, while this enrichment of dispersant has little effect on mechanical performance of RBSC products; 3. Sharp edges on surface of raw particles could result to friction among particles, which afford strength to green bodies but prevent particles packing more closely.