The invention discloses a silica gel hydrophobic modification method achieved under the action of microwaves. Common kiselgel a particles with the pore size of 5 nm to 8 nm are adopted as raw materials; silica gel impurity removal pretreatment is carried out firstly, and then n-heptane, ethyl alcohol and trimethylchlorosilane are prepared into a silane modifier according to a certain proportion; pretreated silica gel is immersed in the silane modifier, the microwave effect is used for assisting in silica gel modification, and emifinished lyophobic silica gel is obtained; finally, the semifinished lyophobic silica gel is washed with n-heptane to remove the residual silane modifier, then filtering, drying and the like are carried out till the weight of the semifinished lyophobic silica gel does not change any more, and finished lyophobic silica gel with good lyophobic effect and adsorption performance is obtained.