On-site weather service is an important part of meteorological service. It is well-targeted, and has remarkable characteristics of great flexibility and high responsibility in the practical work. Learning from the on-site weather service in three Olympic activities in 2008, we can find that on-site weather service has taken an important place in the large-scale events. For the meteorologists, on-site weather service work is not only a challenge against their current techniques and capabilities, but also a chance for them to show public meteorological science and bring their forecasting abilities to a higher level.