Abstract: A fan rotor assembly has an inner rotor, an outer rotor, a central retainer and a central shaft. The inner rotor has multiple first blades. The outer rotor is stacked on the inner rotor and has multiple second blades. The central retainer is mounted through the inner and outer retainers. The central shaft is mounted in the central retainer under the inner rotor. The fan rotor assembly with first and second blades provides excellent airflow.