During the flood period of 1999 a simultaneous hydrometry, on the largest-scale and the fullest-items in history, was carried out in the downstream of Xijiang River, Beijiang River and the net rivers of Pearl River delta. This paper presented briefly the simultaneous hydrometry. After analyzing rationality of the results, the paper expounded the precision of the hydrometry, the boundary conditions of upstream and downstream and therepresentation of flood-tide. Furthermore, the paper put forward the change of water distribution proportion of main river nodes in Pearl River delta and Eight Estuaries, including its influence in hydrologic cycle.