Rapid actin turnover is essential for numerous actin-based processes. However, how it is precisely modified remains poorly understood. AIP1 has been shown to be an important factor by acting coordinately with ADF/cofilin in promoting actin depolymerization, the rate-limiting factor in actin turnover. However, the molecular mechanism by which AIP1 promotes actin turnover remains largely unknown in plants. Here, we provide the demonstration that AIP1 promotes actin turnover, which is required for optimal growth of rice plants. Specific downregulation of OsAIP1 increased the level of filamentous actin and reduced actin turnover, whereas overexpression of OsAIP1 induced fragmentation and depolymerization of actin filaments and enhanced actin turnover. In vitro biochemical characterization showed that, though OsAIP1 alone does not affect actin dynamics, it enhances ADF-mediated actin depolymerization. It also caps filament barbed end in the presence of ADF, but the capping activity is not required for their coordinating action. Real-time visualization of single filament dynamics showed that OsAIP1 enhanced ADF-mediated severing and pointed end subunit dissociation. Consistent with this, the filament severing frequency and subunit off-rate were enhanced in OsAIP1 OE but decreased in RNAi protoplasts. Importantly, OsAIP1 acts coordinately with ADF and profilin to induce massive net actin depolymerization, indicating that AIP1 is a major player in the turnover of actin, which is required for optimizing F-actin levels in plants.