Abstract: Annular fuel is a new type fuel which can improve reactor safety and economics on a large scale. The annular fuel reactor is an advanced type reactor. A small annular fuel reactor has been study and designed, and calculating soft and calculating method fitting for this reactor has been empoldered., too. Especially, the method of calculating reactor core few group parameters introducing regarding whole assembly as a cluster improves precision of calculation so much. Addition, some core key parameters has been calculated. For example,calculating reactor core keff,the per worth and gross worth of all control poison, the temperature reactivity swing and so on. So that the resulting indicates that the annular fuel reactor has been proven to be stable and safe. It can be a new generation reactor.