Due to the load-balancing and parallelism of parallel switches, high-speed arrived packets (or cells) with same destination will be spread into many low speed switching fabrics for processing. When these packets are sent to the output, their sequence cannot be guaranteed. This paper proposes a structure of Virtual Input Queues (VIO) and a scheduling algorithm named Sequence Keeping Round-robin (SKRR), and simultaneously evaluates the throughput and the average delay performance for this technique in theory.