In view of carrier injection unbalance problem of the quantum dots (QDs) ligh t emitting diode (QLED),the mechanism of carrier injection is studied in this paper.Models based on the Folw er-Nordheim (FN) tunneling injection and space-charge limited current (SCLC) conduction are simulated to a nalyze the injection situation of holes and electrons in the QDs layer,and samples of QLED are fabr icated.CdSe/CdS is used as QDs layer,poly(ethylenedioxythiophene):polystyrenesul phonate(PEDOT:PSS)is used as hole injection layer (HIL),N,N/-bis(3-methylphenyl)-N,N/-bis(phenyl)benzidine (TPD) is used as hole transport layer (HTL),and tris-(8-hydroxyquinoline) aluminum (Alq₃) is used as electron transport laye r (ETL).With the thickness of QDs being fixed as 25nm,the optimal thicknesses of TPD and Alq_3are respectively confirmed to be 48nm and 22nm.The simulation results show that when the applied voltage is less than 6.5V,the carrier transport process follows the pattern of the FN tunneling injection,otherwise,it follows the pattern of the SC LC.Experimental results show that the QLED exhibits red light when the Alq_3thickness is 20nm,and the green light b egins to appear with the increase of the Alq_3thickness.The experiment results are basically agree with the simulat ion results.