Low Carbon Magnesia Carbon Brick were prepared with Fused Magnesia and Nature Flake Graphite as raw materials, Phenolic Resin as bonding agent, and Aluminum Metal powder as antioxidants. According to the theory of dense granules of continuous Andreassen formula, the effects of three kinds of critical particle of Magnesia clinker and particle size distribution coefficient on properties of Low Carbon Magnesia Carbon Brick, including thermal expansion ratio, oxidation resistance and slag resistance, were studied. The results showed that by choosing the proper magnesia critical particle size and adjusting the particle gradation, contacting surface area between the graphite and magnesia can be increased, and the thermal expansion stress of magnesia at high temperature can be reduced therefore the properties of Low Carbon Magnesia Carbon Brick are improved.