The application of upconversion (UC) materials, especially in solar cells, is still constrained because of their lower UC efficiency. In this work, co-doped Li + was used to enhance the UC luminescence of β-NaYF 4 :Er 3+ /Yb 3+ microcrystals. The influence of Li + on the quenching concentration of Er 3+ was investigated. The UC emission intensity was significantly improved by introducing different concentrations of Li + ions. After 4mol% Li + doping, the quenching concentration of Er 3+ increases from 2% to 4mol%. Meanwhile, the green and red emission is enhanced 2 and 3.3 times, respectively. The results indicate that both the emission intensity and the quenching concentration can be increased by Li + doping.