A method for cutting off a fin in a field effect transistor, comprising: step 1: forming fins and first spacing regions, there are two types of fins—the first type is configured to be cut off and a second type is configured to be reserved; and forming a first material layer to fill the first spacing regions; step 2: forming a first pattern structure comprising first strip structures aligning to one first type fin and second spacing regions; step 3: forming second sidewalls on two sides of each first strip structure; step 4: removing the first strip structures to form a second pattern structure by the second sidewalls; step 5: etching away the first material layer and the first type of fins by using the second sidewalls as a mask ; step 6: removing the second sidewalls and the remaining first material layer. The present application enables using less advanced lithography equipment.