利用居地-奥非脱理论计算了Er3+离子在氟化钇锂(LiYF4简写为YLF)晶体中的辐射跃迁几率AJJ′，无辐射跃迁几率ωJJ′及激发态荧光寿命τJ，并根据荧光动力学方程计算出各激发态布居数NJ与掺杂浓度x的关系。对2.7 μm激光(4I11/2→4I13/2)来说，掺杂浓度要大于～3at.％，才能实现布居数反转，对波长为1.73 μm的4I13/2→4I15/2跃迁，存在荧光强度最大的掺杂浓度xop，在泵浦几率为103～105 s-1范围内，xop为1.8～3.0at.％。文中还计算了Er:YAG晶体的光谱特征参数，在相互比较的基础上论述了Er:YLF作为激光晶体的优越性。

The radiative transition probabilities A JJ′ , nonradiative transition probabilities ω JJ′ and fluorescence lifetimes τ J of excited levels of Er 3+ ions in YLF crystal are calculated by using the Judd Ofelt theory. On the basis of equations of fluorescent dynamics the populations w J of excited levels, dependented on doped concentrations x, are calculated too. For 4I 11/2 → 4I 13/2 transition (at wavelength of 2.7 μm), only if doped concentration is bigger than 3 at.% the population inversion can be, and the fluorescence strength and doped concentration are increased. But for 4I13/2→4I15/2 transition (at wavelength of 1.73 μm), there is optimal doped concentration for which the fluorescent strength is maximal. When the pump probability is 103～105 s-1, the xop is 1.8～3.0 at.%. The spectral characteristic parameters of Er3+ ions in YAG crystal are calculated. Based on the comparison the advantages of Er3+:YLF as a laser crystal are discussed.