Abstract: According to the test method of GB/ T 7320.1-2000,the line expansion rate and average expansion coefficient of the silica bricks samples were tested and calculated,the uncertainty factors which influenced the line expansion rate and average expansion coefficient were analyzed. And every uncertainty component which influenced the line expansion rate and average expansion coefficient was calculated and combined. The report of uncertainty for silica bricks was ρ=1.06%,U=0.01%,k=2;α=10.8×10-6℃-1,U=0.1×10-6℃-1,k=2。