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Nowadays, Mn4+-activated fluoride red phosphors with excellent luminescence properties have triggered tremendous attentions for enhancing the performance of white light-emitting diodes (WLEDs). Nonetheless, the poor moisture resistance of these phosphors impedes their commercialization. Herein, we proposed the dual strategies of "solid solution design" and "charge compensation" to design K2Nb1−xMoxF7 novel fluoride solid solution system, and synthesized the Mn4+-activated K2Nb1−xMoxF7 (0 ≤ x ≤ 0.15, x represents the mol % of Mo6+ in the initial solution) red phosphors via co-precipitation method. The doping of Mo6+ not only significantly improve the moisture resistance of the K2NbF7: Mn4+ phosphor without any passivation and surface coating, but also effectively enhance the luminescence properties and thermal stability. In particular, the obtained K2Nb1−xMoxF7: Mn4+ (x = 0.05) phosphor possesses the quantum yield of 47.22% and retains 69.95% of its initial emission intensity at 353 K. Notably, the normalized intensity of the red emission peak (627 nm) for the K2Nb1−xMoxF7: Mn4+ (x = 0.05) phosphor is 86.37% of its initial intensity after immersion for 1440 min, prominently higher than that of the K2NbF7: Mn4+ phosphor. Moreover, a high-performance WLED with high CRI of 88 and low CCT of 3979 K is fabricated by combining blue chip (InGaN), yellow phosphor (Y3Al5O12: Ce3+) and the K2Nb1−xMoxF7: Mn4+ (x = 0.05) red phosphor. Our findings convincingly demonstrate that the K2Nb1−xMoxF7: Mn4+ phosphors have a good practical application in WLEDs. [ABSTRACT FROM AUTHOR]