Abstract: The self-bred muskmelon variety ‘Ganlu No.6’ was used as the experimental material with seven topdressing potassium fertilizer treatments, the effect of topdressing K quantity on yield, quality and photosynthesis of oriental melon in solar greenhouse was explored, and the best topdressing amount of potassium fertilizer was determine, in order to provide reference for the scientific and rational application of potassium fertilizer in thin-skinned melon.The results showed that the chlorophyll content, photosynthetic characteristics, soluble solids, sugar content, vitamin C and soluble protein content and yield all reached the maximum value when the topdressing K quantity was 184.5 kg·hm^-2.Therefore, under the condition of substrate cultivation in solar greenhouse, when the fertilizer amount was N 112.5 kg·hm^-2,P₂O₅ 225 kg·hm^-2,K₂O 112.5 kg·hm^-2 first and 184.5 kg·hm^-2 later, it was beneficial to improve the photosynthesis, yield and nutritional quality of oriental melon.