Sufficient and necessary conditions for the embeddings between Besov spaces B s 1 p,q and modulation spaces M s 2 p,q are obtained. Moreover, using the frequency-uniform decomposition method, we study the Cauchy problem for the generalized BO, KdV and NLS equations, for which the global well-posedness of solutions with the small rough data in certain modulation spaces M s 2,1 is shown.