The influence of atomic coherence on the formation of a ultracold molecule from ultracold two-state atoms is discussed via photoassociation.By using the method of quantum statistics,it is found that under the action of atomic coherence,the molecular number vibrates with an approximate period and with reduced amplitude.Atomic coherence has a strong influence on the temporary of the whole photoassociation process,but the molecules are always subject to sub-Poisson statistical distribution.