In order to study the structural performance relationship of quantum dot light emitting devices. Quantum dot light emitting diodes (QLEDs) were fabricated in this paper using CdSe/ZnS quantum dot as the light-emitting layer (EL), poly-TPD as the hole transport layer (HTL), Alq3 as the electron transport layer (ETL). Experiment results show that the QLEDs fabricated have a low turn on voltage and high color purity.The structure and the performance parameters of the device were measured and the results showed that the QLEDs fabricated had a low turn on voltage and high color purity. According to the measured thickness of HTL, EL and ETL, the tunneling model as well as the space charge limited current model (SCLC) were put into use to analyze the experimental results. The carrier injection and transport mechanism were studied through the models. The simulation results showed that the thickness of each film would influence the injection and transportation of carriers inside the QLED. In the meanwhile, we also noticed from the simulation results that there was a transition voltage, when the applied voltage was lower than the transition voltage, the carrier injection inside the QLED was mainly confirmed with the tunneling model; when the applied voltage was higher than the transition voltage, the carrier transportation inside the QLED was mainly confirmed with the SCLC model. The rationality of the models was proved through the experiment results which can be helpful to optimize the thickness of every film as well as to improve device performance.