Real-time　tasks　scheduling　is　key　problem　in　real-time　system,　real-time　dynamic　scheduling　is　main　aspect　of　real-time　scheduling.　When　real-time　scheduling　is　used　in　practical　system　it　may　just　use　limited　number　of　priority　level.　When　real-time　scheduling　theory　carry　out　theoretic　analysis,　all　of　them　assume　that　there　are　unlimited　number　of　priority　level.　The　paper　presents　the　algorithm　of　dynamic　real-time　scheduling　in　the　condition　of　limited　priority　level,　and　presents　the　minimum　number　of　priority　level　that　the　tasks　system　schedules　dynamically.　Finally,　the　algorithm　complexity　is　analyzed.