Stalagmite oxygen isotope (δ¹⁸O) record has been widely used in characterizing Asian Monsoon variations. In southwest (SW) China, although the stalagmite δ¹⁸O was usually suggested as a precipitation proxy, it remains a subject of debate. Here we present two replicated, high-precise-dated stalagmite δ¹⁸O records for the interval 1710–2003 AD from Yunnan province, SW China. The stalagmite δ¹⁸O shows no correlation with the local monsoon precipitation, but a significantly positive correlation with the Pacific Decadal Oscillation (PDO) index. It demonstrates that the stalagmite δ¹⁸O in SW China is most likely influenced by the atmospheric circulation associated with the PDO through the upstream depletion mechanism. During the warm (cold) PDO period, the deficit rainfall over India would make the δ¹⁸O of water vapor transporting to SW China less (more) negative due to the weaker Rayleigh distillation process, which would lead to the less (more) negative stalagmite δ¹⁸O. Consequently, the stalagmite δ¹⁸O in SW China is suitable to reconstruct the PDO variations. It is important to note that the other factors, such as El Niño–Southern Oscillation (ENSO) or sea surface temperature (SST) also possibly affect the stalagmite δ¹⁸O in SW China, and the relationship between them requires further studies.