The present disclosure generally relates to a multi-leaf collimator. The multi-leaf collimator may include a set of leaves installed in a cavity, each leaf of the set of leaves having a length along a first direction. At least a portion of the set of leaves may extend beyond the cavity along the first direction. The set of leaves may be arranged along a second direction, the second direction being different from the first direction. A length of a target leaf of the set of leaves may be less than a length of a reference leaf of the set of leaves. The target leaf may be located in an end portion of the set of leaves along the second direction. The length of the set of leaves may conform to the shape of a maximum therapeutic radiation field.