Abstract. Precipitation/humidity proxies are widely used to reconstruct the historical East Asian summer monsoon (EASM) variation based on the assumption that summer precipitation over eastern China is closely and stably linked to the strength of EASM. However, whether the observed EASM-precipitation relationship (e.g., increased precipitation with a stronger EASM) was stable throughout the past time remains unclear. In this study, we used model outputs from the Paleoclimate Modelling Intercomparison Project Phase Ⅲ and Community Earth System Model to investigate the stability of the EASM-precipitation relationship over the last millennium on different timescales. The model results indicate that the EASM strength (defined as the regionally averaged meridional wind) enhanced in the Medieval Climate Anomaly (MCA; ~ 950–1250 A.D.), during which there was increased precipitation over eastern China, and weakened during the Little Ice Age (LIA; ~ 1500‒1800 A.D.), during which there was decreased precipitation, consistent with precipitation/humidity proxies. However, the simulated EASM-precipitation relationship is only stable on a centennial and longer timescale and is unstable on a multi-decadal timescale. The nonstationary multi-decadal EASM-precipitation relationship broadly exhibits a quasi-60-year period, which may be attributed to the internal variability of the climate system and have no significant correlation to external forcings. Our results have implications for understanding the discrepancy among various EASM proxies on a multi-decadal timescale and highlight the need to rethink reconstructed decadal EASM variations based on precipitation/humidity proxies.