Based on the HYSPLIT model, a Lagrangian particle dispersion model, combined with E-R (evaporation minus precipitation) diagnostics and the related quantitative analysis method of water vapour contribution, the water vapour source and transport characteristics of extreme precipitation in Shandong Province affected by Rumbia (August 2018) are diagnosed. Results indicate that the occurrence of extreme precipitation was related to global water vapour transport and convergence. The water vapour of extreme precipitation mainly came from the regions of the Indian Ocean-Bay of Bengal-South China Sea, the lowlatitude western Pacific, the Mid-latitude Northwest Pacific and Eastern China. The low-latitude western Pacific made the largest contribution, followed by the Mid-latitude Northwest Pacific, while the Indian Ocean-Bay of Bengal-South China Sea and Eastern China both contributed similar amounts that were less than those from the Mid-latitude Northwest Pacific. Besides, by comparing with differences of water vapour transport in different source regions, it is found that although the uptake from the region of the Indian Ocean-Bay of Bengal-South China Sea was relatively high, its ultimate contribution to the target precipitation was dramatically reduced due to evaporation in the air parcels. Despite the uptake from the Mid-latitude Northwest Pacific and Eastern China were relatively low. Still, moisture loss in transit was also small, and the released proportion from the former was higher, so their contribution cannot be ignored.