Humidity has an important influence on the strength of the silica (SiO2). We examine the influence of liquid water on the tensile properties of amorphous silica (a-SiO2) using reactive molecular dynamics simulation. The results of the quasi-static tension show that liquid water reduces the tensile strength of a-SiO2 significantly. The tensile strength of dry a-SiO2 is 9.4 GPa while the tensile strength of a-SiO2 in the presence of liquid water is only 4.7 GPa. The strain-stress curve of dry a-SiO2 indicates that the stiffness of the a-SiO2 structure becomes stable with the increase of strain. On the other hand, the stiffness of the a-SiO2 with liquid water is gradually reduced with the increase of tensile strain. Moreover, the strain-stress curve of a-SiO2 in a strain range of 16% to 20% in the presence of liquid water is similar to the yielding phenomenon of plastic metal. The snapshots of the a-SiO2 in the presence of liquid water during the tension show that no plastic deformation is observed. We propose that the stress-enhanced hydrolysis releases part of the stress for the rupture of the Si–O bonds, so that the stiffness of the a-SiO2 in the presence of liquid water decreases with the increase of strain.