To address the problem that the real-time multimedia I/O is the bottleneck of the transparent computing system performance, this paper proposed a multimedia I/O access control policy for transparent, called CAVIO (Classification and Aggregation-based Virtual I/O mechanism).CAVIO classifies I/O requests by their types to give the multimedia I/O a high priority, aggregates the small I/O to reduce the average path length and the network processing overhead, and carries out network transmission concurrently to improve the disk I/O throughput over network.The experiment results demonstrate that CAVIO significantly improves the multimedia I/O processing performance in transparent computing system.