The mid-latitude arid region of Central Asia (CA) served as a pivotal corridor for prehistoric trans-Eurasian cultural exchange along the ancient Silk Road. While hydroclimate variability is widely recognized as critical for regulating Silk Road dynamics, the mid-to late-Holocene hydroclimate evolution in CA remains debated. Here, we present a high-resolution diatom record from Lake Xiaolongchi in the central Tianshan Mountains to reconstruct hydroclimate variability over the past similar to 8 kyr. Our findings reveal a distinct transition from arid mid-Holocene conditions to a wetter late Holocene, indicated by a rising planktonic/benthic diatom ratio. Within this generally arid mid-Holocene period, a significant megadrought occurred between 6 and 5 cal ka BP, characterized by a pronounced decline in planktonic diatoms alongside increases in benthic and epiphytic diatoms, notably Achnanthidium minutissimum. Temporally, this megadrought coincides with drought events in western CA, a winter precipitation-dominated region, suggesting pan-regional aridification across the region. We propose that this prolonged megadrought likely disrupted lowland oasis ecosystems, potentially resulting in the northwards displacement of trans-Eurasian exchange routes towards Eurasian steppe corridors. Moreover, the notable increase in moisture after similar to 4 cal ka BP coincided with late Holocene piedmont oasis formation. Moisture recovery during this period likely facilitated the emergence of agro-pastoral societies, thereby laying the foundation for the organized Silk Roads.