Nanoscale zerovalent iron@mesoporous silica (NZVI@mSiO₂) can effectively remove chlorinated hydrocarbons in groundwater. The effects of the reaction time after adding silicon source and the amount of silicon source added in the structure of NZVI@mSiO₂ were studied. 1,1,1-TCA was used as a model chlorinated hydrocarbon to study the effects of NZVI@mSiO₂ amount and natural organic matter (NOM) on the removal of chlorinated hydrocarbons via the adsorption and adsorption-degradation by NZVI@mSiO₂. The results show:the stable structure of NZVI@mSiO₂ can be obtained after adding tetraethoxysilane (TEOS) and stirring at 300 r/min for 4 h; the thickness of the mSiO₂ shell can be controlled by adding different amount of TEOS; higher NZVI@mSiO₂ dosage provides more active sites for the reaction, which is beneficial to the removal of chlorinated hydrocarbons via the adsorption-degradation; NOM can reduce the stability of mSiO₂ suspension through bridging and trapping mSiO₂ particles, while the introduced new sites and the reduced pH value of the solution finally promote the removal of chlorinated hydrocarbons via the adsorption and adsorption-degradation.