This　study　investigates　the　impact　of　opening　a　high-speed　railway　(HSR)　on　the　innovation　output　of　offsite　subsidiaries　in　China.　Our　findings　suggest　that　the　innovation　output　of　offsite　subsidiaries　increases　significantly　after　the　opening　of　HSR　between　the　cities　in　which　the　listed　firms　and　their　subsidiaries　are　located,　and　the　results　are　robust　after　a　series　of　robustness　checks.　Hence,　the　spatiotemporal　squeezing　effect　generated　by　opening　HSR　significantly　improves　the　efficiency　of　information　exchange　and　resource　sharing　between　parent　and　subsidiary　companies,　which　greatly　promotes　the　innovation　output　of　offsite　subsidiaries.