Phosphorus (P) as a basic mineral nutrient is considered to constrain primary productivity in many tropical and subtropical forests. Soil phosphatase plays a very important role in P cycling in forest ecosystems because it catalyzes the hydrolysis of soil organic P compounds (e.g., nucleic acids and phospholipids) into forms that are available to plants and soil microbes. Soil phosphatase activity is widely considered an effective indicator of the P demand of plants and microbes due to its ability to mediate plant and microbial nutrient acquisition from organic P compounds. In recent decades, increasing nitrogen (N) deposition due to human activity has been demonstrated to cause soil P deficiency and increase soil acid phosphomonoesterase activity (APA) in several tropical or subtropical forests. However, little is known about the effects of N deposition on soil APA in other forest types (e.g., broadleaf forest and coniferous forest) or whether P addition may relieve soil P limitation in these forests. The present study investigated the responses of soil APA to N and P additions in a monsoon evergreen broadleaf forest (MEBF), a Pinus massoniana forest (PF), and a mixed broadleaf and pine forest (MF) in Dinghushan Mountain, Guangdong Province of southern China via a six-year fertilization experiment. The experiment used full factorial design, including four treatments:control (no fertilization), N addition (150 kg N hm^-2 a^-1), P addition (150 kg P hm^-2 a^-1), and combined N and P addition (150 kg N hm^-2 a^-1 plus 150 kg P hm^-2 a^-1). Each 5 m × 5 m plot was established with a surrounding buffer strip (5 m wide). For each N and P application, NH₄NO₃ and NaH₂PO₄ solutions were applied below the canopy with a backpack sprayer, every other month from January 2007 to July 2013. In July 2013, soil samples were collected for analysis. Results showed that soil APA was significantly higher in MEBF ((15.83±2.46) μmol g^-1 h^-1) than that in MF ((10.71±0.78) μmol g^-1 h^-1) or PF ((9.12±0.38) μmol g^-1 h^-1) soils, and a significant negative correlation existed between soil APA and soil available P contents in all forest types. N addition significantly increased soil APA in MEBF, while no statistical difference was found in MF or PF. P addition significantly decreased soil APA in MF and PF, but had no significant effect in MEBF. Combined N and P addition notably depressed soil APA in PF, but had no significant influence in MEBF and MF. Importantly, interactions between N and P additions were observed in MEBF. Based on our results, N deposition is expected to aggravate soil P deficiency in mature subtropical forest, while the N-induced P-limited state of these forests might be effectively relieved by P addition. In conclusion, the addition of P fertilizer may serve as an effective method for the sustainable future development of tropical and subtropical forests.