A nonconventional gas centrifuge cascade, called the NFSW (no feed and single withdrawal) cascade, is studied in the separation of middle components by means of numerical simulation. The cascade has no feed and only a single withdrawal at either end of the cascade, different from conventional cascades, which usually have two withdrawals at the two ends of the cascade and one feed in between. The material to be separated is loaded in a reservoir at either end, and the desired component is enriched in either the reservoir or the withdrawal at the other end. The effects of the unit separation factor (equivalently, the cascade length) and the ratio of the upstreaming flow rate to the withdrawal rate are investigated on separation. The separation performance is evaluated in terms of the material recovery and the operation time efficiency, and is compared with those of the corresponding conventional cascades and another type of nonconventional cascade, the SW (single withdrawal) cascade. It is found that the NFSW cascade is superior to the conventional cascade and comparable in the material recovery with, but advantageous in the operation time efficiency over the SW cascade.