The sites in Heilongjiang province have been covered by flood waters from the Heilong River, Liu Min of the Dinosaur National Geology Park told China's state-run Xinhua news agency.
Dikes built near the mountains in recent years failed to keep back the flood waters, Liu said.
Flooding from the river also inundated the Heilong River Basin Museum beginning Aug. 17 and has reached 3 feet deep in some of the museum's rooms, museum curator Zhao Yong said.
More than 2,000 exhibit items on the first floor have been moved to the second floor, he said.
At the excavation sites there were fears fossils could be loosened and washed away after being soaked for a long period of time, a park employee said.
The 15-square-mile park, where several hundred fossilized dinosaur skeletons are believed to be buried underground, opened in 2002.