The invention discloses a silicon etching method which is used for etching silicon grooves with different width sizes on a silicon substrate. The silicon etching method comprises the following steps: S1, providing the silicon substrate; S2, depositing a mask layer on the silicon substrate; S3, corroding the mask layer to form windows with the different width sizes; reserving the mask layer with the certain thickness at the bottom of the window which does not have the smallest width size at least to meet the requirements that the depths of all the silicon grooves are the same after the step S4; and S4, corroding the mask layer and the silicon substrate at the bottoms of the windows to form the silicon grooves. According to the silicon etching method, the mask layer with the certain thickness is reserved at the bottom of the window which does not have the smallest width size and the mask layer with the certain thickness is used for protecting the larger window; the small window is firstly etched to realize that the depths of the finally-obtained silicon grooves are the same.