Microstructure on the ladle, Decarbonization converter devices and low-pressure conditions, the use of magnesia-carbon refractories the oxidation rate to a certain extent, therefore, these magnesium carbon refractories the microstructure to improve its oxidation resistance is very helpful. Japan casting, forging company staff using precise determination of the equilibrium of magnesia-carbon refractories cubic spline block the oxidation rate, Study of the largest particle size magnesia and magnesium oxide carbon refractories relationship between the rate. Experimental cubic spline block (20 × 20 × 20mm) from Kurosaki broadcast mill companies. Sample the chemical composition and particle size distribution the following table. Sample M5 - 1 M5 - 3 particle size distribution, mm magnesium content of 3.0% ~ ~ 1.0 30.0 1.0 0.5 47.5 20.0 0.5 - 0.2 19.0 25.0 "0.2 28.5 20.0 5.0 graphite content of 5.0% respectively in the experimental fabrication Pressure to 3.7 × 10  thickness and 2.1 × 10  under electron. Temperature at 120 0 ° C ~ 1400 ℃. According to an oxidation process simulation of the partial oxidation reaction, through the weight loss sample to analyze its oxidation rate. The experimental results obtained : oxygen decarburization layer through the stomata-proliferation. The oxygen is 2.1 × 10  ion circumstances, M5 - 3 (magnesia largest particle size of 3.0 mm) sample of effective oxygen diffusion rate than M5 - 1 (the largest magnesia particle size of 1.0 mm) slightly lower. In 1400 ℃ M5 - 3 and M5 - 1 of the effective oxygen diffusion rate of occurrence decreased significantly. Found by optical microscopy decarbonization layer appeared dense layer, This is probably because the M5 - 3 channel pore over M5 - 1 of twists and turns and M5 - 3 specimen than M5 - 1 specimen easier to form a dense layer.