It really depends on what kind of weather you like. Generally speaking, China's seasons are similar to our own but are more extreme - hotter in the summer and colder in the winter. So you might find that spring or autumn would suit you best.

Click on this link to the BBC weather pages and you can see more detail about average temperatures and rainfall throughout the year:

http://news.bbc.co.uk/weather/forecast/90?&search=beijing&itemsPerPage=10®ion=world 

Kind regards

Olly, your editor