Millet agriculture was foundational to the emergence of complex societies in Neolithic East Asia, yet the environmental mechanisms shaping its spatiotemporal development remain unresolved. Here, we present a high-resolution reconstruction of Holocene growing-season soil temperature from biomarker proxies in a precisely dated loess sequence from the central Chinese Loess Plateau. Our data reveal a pronounced similar to 3 degrees C soil cooling between similar to 7.5 to 6.0 thousand years B.P. (kyr B.P.), followed by rapid warming and millennia-long relatively stable conditions. By integrating archaeological datasets with transient climate simulations, we show that this mid-Holocene soil cooling which reflects coupled climatic forcing and vegetation-related land surface changes likely compressed the thermally suitable niche for frost-sensitive millets, contributing to a southward displacement of cultivation and delaying large-scale agricultural expansion until the subsequent soil temperature recovery after similar to 6.0 kyr B.P. These findings suggest that large-amplitude soil temperature fluctuations acted as a modulating climatic constraint on the geographic distribution and development trajectory of millet agriculture in East Asia, providing refined insights into climate-society interactions during the Neolithic.