To explore the impacts of precipitation pattern change on forest growth and carbon sequestration under climate change, a manipulation experiment of throughfall reduction was conducted in a Pinus massoniana plantation in southern subtropical China since 2012, which included three 20 m×20 m plots with a 50% throughfall exclusion and their respective control plots. Litterfall samples were collected from January to December every two months in 2016, from five 1 m×1 m aboveground (40 cm) litterfall traps in each plot, and were separated into different components to measure the mass percentage, biomass, and basic chemical properties. The results showed that litterfall quantity and the proportion of needles were both significantly higher than other litterfall components in the plantation (P < 0.05). The short-term manipulated drought did not significantly affect the needle quantity or total litterfall (P > 0.05). Compared to the control, the throughfall treatment enhanced the C content of needle litterfall and N content of fruit litterfall by 27.4 g/kg and 5.1 g/kg, respectively (P < 0.05). The treatment also increased the lignin content of needle litterfall, cellulose content of broadleaf litterfall, hemicellulose content of skin litterfall by 3.9%, 5.2%, and 4.0%, respectively, while it decreased the C and cellulose content of skin litterfall as well as the C:N ratio of fruit litterfall (P < 0.05). The positive correlations between the N and P content of the litterfall, and between the C and lignin content of the litterfall, were both significant (P < 0.05). These results indicated that the short-term experimental throughfall reduction did not significantly alter total litterfall, while it increased the lignin and C content of needle litterfall, in a southern subtropical P. massoniana plantation. Our study further suggests a possible decrease in the decomposition ability of litterfall, which could reduce the input of litter-derived soil carbon in a southern subtropical P. massoniana plantation, under short-term manipulated drought conditions.