A new large mesoporous material made from commercially available poly(ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) type triblock copolymer as template was presented, in which the pore size is larger than the pore size of ordinary MCM-41. How to control the size of this proposed mesoporous silicate thin films by synthesis conditions is discussed. The size control has two means. One is the pore size control and the other is the thickness control of the silica framework. The mesoporous silicate thin films are synthesized using only EO20-PO70-EO20 type of triblock copolymer as template by spin coating.