Presumably, this title means that these are cities where people say they feel happy. Many countries seem to run these survey results from time to time. There's even one in Aussieland. Can't remember which city got the gong, though.
In the Chinese survey, they measured indices such as income, expenditure, social security, and life quality.
The city that seems to have received the top spot is Haikou on the island of Hainan (Not far from Vietnam). With a semi-tropical climate it would be a nice place to live.