Let (R, m) be a local ring of prime characteristic p and of dimension d with the embedding dimension v. Suppose the Frobenius test exponent for parameter ideals F te(R) of R is finite, and let Q = p F te(R) . It is shown thatWe also improve the bound for F -nilpotent rings. Our result extends the main results of Huneke and Watanabe [6] and of Katzman and Zhang [9].