International Labor Day falls on May first and depending on when it falls, workers might get an "extension". So, for example, if May 1 is a Saturday, the public will get an extension and have Monday, May 3 off.
Travel during National Holidays:
Many workers may extend the weekend to make it a longer holiday which can translate into millions of Chinese traveling domestically and internationally. Travel fares double and triple and advance bookings must be made weeks, even months ahead for international travel. Hoards of tour groups flock to the major tourist destinations of China, so you can forget having a quite moment to ponder how the Great Wall was built.
May Holiday Travels:
If you can avoid it, it's advisable not to travel domestically during the week around May 1st. According to 2004 statistics, 90 million tourists were expected to travel; in 2006, China’s main tourist destinations saw a 17% increase in visitors. Four million tourists traveled to Shanghai alone.