The effective relations of silica (SiO2) Concentration in boiler drum and generated steam, with respect to pH and pressure for a natural circulation water wall tubes (WWTs) high-pressure (158 and 100 kG(r) cm(-2)) boiler, (Type TGME-206-COB, Russia) at Ghorasal Thermal Power Station (GTPS) Bangladesh, has been Studied. Extensive analyses of different parameters of boiler water chemical regime (WCR) of the plant based experimental results revealed that on maintaining SiO2 0.35 (+/- 0.15) mgL(-1) in boiler drum clean (evaporation) section [at pH 9.1 (+/- 0.1), temperature 330 degrees C (+/- 10 degrees C)] of boiler WCR provides excellent results with less corrosion or scale formation in interior Surface of boiler WWTs and turbine blades. Such a procedure is effective for high softening of make up water SiO2 0.02 (+/- 0.01 mgL(-1)) ensuring high degree of purity of feed water cycle of the boiler and appropriate dosing of chemicals in boiler.