Existing Ethernet Passive Optical Network (EPON) Dynamic Bandwidth Allocation (DBA) algorithms suffer from the disadvantage of idle time loss, which lower the upstream bandwidth utilization. This letter proposes an improved upstream transmission scheme with idle-time eliminating mechanism. Theoretical analysis and numerical calculation prove that the improved scheme can effectively eliminate the idle time and enhance the efficiency of upstream link utilization. Simulation results have shown that the bandwidth utilization can be raised up to 15% in heavy-load scenarios while the time delay performance of Assured Forwarding (AF) and Best Effort (BE) services are improved simultaneously.