Environmental factors affecting the SiO2 content change of glass fiber caused by the acid solution method were experimented and investigated, and the following results were obtained by analyzing the kinds of acid, concentration, treating time and temperature. 1. In the acid treatment, plain weave showed the maximum value, 97% of SiO2 content in conditions where HC1 concentration was 3N, treating time 95 minutes and treating temperature was 9$0^{circ}C$, while 5-H satin showed the maximum value, 96% of SiO2 content where HC1 concentration was 3N, treating time 90 minutes and treating temperature was 8$0^{circ}C$. 2. Respectively 1% increment of SiO2 content was shown for both cases in which plain weave was water-cleansed for 15 minutes in hot water of 7$0^{circ}C$, following the acid treatment and 5-H satin for 17 minutes. 3. 1 or 2% of A12O3 is remained after water-cleansing, because ionic bonding is lagrer than that of other metallic oxide compounds and so perfect ionization is impossible. 4. Fiber structure was the most stable when it was heat-treated at 80$0^{circ}C$ for 60 minutes.