Antireflective coatings prepared by sol gel method are importantly used in high power laser devices, the stability of colloidal, laser induced damage thresholds (LIDTs) and antireflective efficiencies of coatings resulted from different particle sizes silica colloidal suspensions and silica antireflective coatings are studied by controlling different molar ratios of water and tetraethoxysilane (TEOS). The results show that the transmittance of porous silica antireflective films is higher than 99.5% and LIDTs are greater than 62 J/cm2 (1064 nm, 15 ns), the transmittance and LIDTs of smaller particle size silica antireflective film reaches 99.75% and 77.42 J/cm2 (1064 nm, 15 ns), respectively. The average particle sizes of colloidal suspensions increase with the mol ratio of H2OTEOS, the particle size quickly increases when the molar ratio of water and ester is greater than 3.5. The solution with particle size below 10 nm has excellent stability, and the particle size and viscosity of the solution is almost not unchanged. The stability of films with different particle sizes in different humidities is researched, all the films′ transmittance in high humidity drops and the film with larger particle size has more obvious decrease in transmittance, and therefore the chemical films are more suitable for the use in low humidity environment.