The porous borosilicate membranes were prepared from Si(OC2H5)4-(CH3O)3B-H2O-C2H5OH system by sol-gel method. For investigation the characteristics of gels and porous borosilicate membrane. We examined gels and porous borosilicate membrane using X-ray diffractometer, IR spectrophotometer, BET and TG-DTA. The Optimum mole ratio of Si(OC2H5)4 : (CH3O)3B : H2O : C2H5OH for porous borosilicate membrane was 1 : 0.11 : 5.385 : 5.385. The surface area of sintered gel was 244.478(m(2)/g) to 648.138 m(2)/g at 25 ℃ to 800 ℃. The median pore diameter was 0.0034 μm to 0.0052 μm at 25 ℃ to 800 ℃. The particle size of sintered gel was 7 nm to 35 nm at 25 ℃ to 800 ℃.