question: BACKGROUND: Prior to Wuhan lock-down in 2020, chunyun, the largest population mobility on this planet, had begun We quantified impact of Wuhan lock-down on COVID-19 spread during chunyun across the nation METHODS: During the period of January 1 to February 9, 2020, a total of 40,278 confirmed COVID-19 cases from 319 municipalities in mainland China were considered in this study The cross-coupled meta-population methods were employed using between-city Baidu migration index We modelled four scenarios of geographic spread of COVID-19 including the presence of both chunyun and lock-down (baseline);lock-down without chunyun (scenario 1);chunyun without lock-down (scenario 2);and the absence of both chunyun and lock-down (scenario 3) RESULTS: Compared with the baseline, scenario 1 resulted in 3 84% less cases by February 9 while scenario 2 and 3 resulted in 20 22 and 32 46% more cases by February 9 The geographic distribution of cases revealed that chunyun facilitated the COVID-19 spread in the majority but not all cities, and the effectiveness of Wuhan lock-down was offset by chunyun Impacts of Wuhan lock-down during chunyun on the COVID-19 spread demonstrated heterogenetic geographic patterns CONCLUSION: Our results strongly supported the travel restriction as one of the effective responses and highlighted the importance of developing area-specific rather than universal countermeasures