Objective The study aims to explore the change law of fruit quality of the main citrus varieties in Ruili area of Yunnan Province during maturity, offering a theoretical foundation for identifying the appropriate time for fruit harvesting.

Method Four citrus varieties including Orah, Bingtang, Murcott, and W·Murcott were used as tested materials. Fruits were harvested 150-330 d after flowering (August 12, 2020 to February 8, 2021) and 240-405 d after flowering (November 8, 2021 to April 28, 2022). Samples were taken every fifteen days routinely, and the quality of the fruits was determined.

Result The single fruit quality and the fruit horizontal and longitudinal diameters of the four citrus varieties exhibited a trend of growing first and then flattening as the maturity of fruits. Orah, Bingtang, Murcott and W·Murcott fruits terminated their rapid growth and expansion period before 270, 255, 300 and 285 days after flowering, respectively. In a span of two years, except for Murcott (with transition period being consistent in the first and the second year), the color transition period of W·Murcott peel was earlier in the first year, and the color transition period of Orah and Bingtang was later than the first year. Bingtang, Orah, Murcott and W·Murcott all showed stable mass fractions of total soluble solids content (TSS) after 240, 315, 300 and 270 days of flowering, respectively; while the mass fractions of titratable acid content (TA) showed no significant change at 180, 210, 240 and 240 d of flowering, respectively.

Conclusion Combining the indicators such as single fruit weight, horizontal and longitudinal diameter, peel colour, and mass fraction of internal substance content, the fruits of Orah, Bingtang, Murcott, and W·Murcott reach harvest maturity at 315, 255, 300, and 285 d after flowering, which are suitable for harvesting.