: An algorithm for one-way hash function construction based on conservative chaotic system is proposed. The plaintext is divided into a group of message blocks by a fixed length and each message block is iterated some times through standard map. Both the iterations results of every round and the plaintext block determine the two initial values and the steps of iterations in next round. Some items of the result in the final round are chosen to be transformed into Hash value of 128 bits. Theoretical analysis and computer simulation show that this algorithm has good effect in irreversibility, weak collision and sensitivity to initial values. The method is safer in security than the Hash function based on lowdimensional dissipative chaotic maps and it is easy to realize.