The world’s largest seasonal migration of people -- otherwise known as China’s annual Spring Festival holiday -- is increasingly slogging its way through airports and spilling outside China’s borders. With the initial wave of passengers already out the door, China’s travel authorities want to make sure everyone behaves.

Mainland Chinese tourists going abroad on packaged tours during the Spring Festival period are expected to hit close to six million, up nearly 50% from four million in 2013, according to an estimate from Ctrip.com,...