以EDTA为络合剂，用水热法合成了Er3+，Tm3+和Yb3+共掺杂的NaYF4纳米晶。XRD和TEM的结果表明：粒径约为30 nm，属于六方晶系。在980 nm半导体激光器激发下，研究了不同Er3+离子掺杂浓度对Tm3+和Er3+离子上转换发光性能的影响，光强与泵浦功率的双对数曲线表明，474，525，539,650 nm的发射均属于双光子过程，408 nm的发射属于三光子过程。讨论了样品的协作敏化和声子辅助共振能量传递的上转换发光机制。

Nanocrystals of up-conversion phosphor Er3+，Tm3+ and Yb3+ co-doped NaYF4 were prepared by hydrothermal method in the prescence of complexing agent EDTA. Under 980 nm diode laser exciting, the impact of different concentration of Er3+ ion on the up-conversion luminescence intensity was discussed.The samples were characterized by transmission electron microscopy and X-ray diffraction, the results showed that hexagonal nanocrystal NaYF4∶Er3+，Tm3+ and Yb3+ was prepared by hydrothermal method. According to the law of luminescence intensity versus excitation power, the 474 nm blue emission, 525 nm and 539 nm green emission, 650 nm red emission are all due to double photon process, while the 408 nm violet emission is a three-photon process. The up-conversion mechanism and processes were also analyzed.