Hash functions have to be with many security properties to meet the demands of various applications. The preimage awareness (PrA), proposed by Dodis et al., is a security property of hash function that lies between being a random oracle (RO) and collision resistance (CR). The virtue of PrA is that Merkle-Damgard (MD) paradigm is PrA preserving and one can realized a PRO hash function through composing a PRO compression function and a PrA hash function. In this paper we prove Stam's two compression functions having PrA property, where one proof is new and another is difference from Lee et al.'s proof.