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A series of glasses with composition 60NaPO 3 -(40- x )CdF 2 - x YF 3 - y Er 2 O 3 were synthesized via melt-quenching methods and subsequently heat-treated to obtain upconversion luminescent glass ceramics containing NaYF 4 :Er crystals. Hexagonal and/or cubic NaYF 4 crystals were controlled to be bred in the glasses by changing the glass composition. The structure evolution driven by crystallization was characterized using advanced solid-state nuclear magnetic resonance (SSNMR) techniques. The SSNMR results reveal that the Y/Na ratio determines the crystalline phases of NaYF 4 precipitated in this glass system. Y 3+ attracts extra F - ions from P 5+ and Cd 2+ during crystallization because of its stronger ability to attract F - ions, leading to most Y 3+ ions being crystallized into the NaYF 4 crystals. The paramagnetic broadening effect of the Er 3+ ions on NMR signals as well as the upconversion luminescence results indicate that, before crystallization, most Er 3+ ions are surrounded by oxygen within the glasses; however, after crystallization, almost all of them enter the NaYF 4 crystals. On the basis of this local structure investigation, a composition design strategy is developed to obtain highly efficient upconversion luminescent glass ceramics.