In this paper, a new model for randomized computation-the Probabilistic Unlimited Register Machine(PURM) which is simpler than the Probabilistic Turing Machine (PTM)[4,5] is given. We prove the equivalence between PURM program and computable PTM. Moreover, by constructing the PURM programs, we get the sufficiant conditions for a random function that can be simulated by PURM program or PTM. At last, some simple properties of PTM and PURM are discussed.