This paper studies the QoS-aware replica placement problem. Although there has been much work on replica placement problem, most of them concerns average system performance and ignores quality assurance issue. Quality assurance is very important, especially in heterogeneous environments. We propose a new heuristic algorithm that determines the positions of replicas in order to satisfy the quality requirements imposed by data requests. The experimental results indicate that the proposed algorithm finds a near-optimal solution effectively and efficiently for algorithm can also adapt to various parallel and distributed environments.