Highly porous silica ceramics with different pore sizes were fabricated by adjusting the mixed surfactants addition.The effect of the pore size on the cold compressive strength and the thermal conductivity of the ceramics was researched.The results show that the smaller pore size can improve the compressive strength and the thermal conductivity.With the mixed surfactants addition increasing from 0.1 mass％ to 0.4 mass％,the porosity is close,in the range of 88.10％-88.31 ％,and the average pore size decreases from 190 μm to 97 μm;the compressive strength is enhanced from 2.97 MPa to 3.55 MPa;and the thermal conductivity decreases from 0.104 W ? m-1·K-1 to 0.089 W ? m-1 ? K-1.