Abstract: "The Investigation on the Panjiang River" is a geographic thesis written by Xu Xiake,on the basis of his on-the-spot investigation,with the purpose of correcting the mistakes in"History of Great Ming Unity" and clarifying the sources and courses of the North Panjing River and the South Panjiang River.Most of the conclusions are right,but there are obvious mistakes owing to the limitation of the times.In addition,there are still some questionable points.For example:1)The exposition about the sources and courses of the North Panjiang River and the South Panjiang River quoted from"Hitory of Great Ming Unity"can not be found in any one of the four editions of"History of Great Ming Unity".2)"History of Great Ming Unity" says that the North Panjiang River and the South Panjiang River join at Pingfaheng Shanzhai. The diary on 24 Sept.1637 in "Xu Xiake’s Travels Travels in West Guangdong.Three" criticized this view seriously.But it can not be known why this criticism is not present in"The Investigation on the Panjiang River". The possible explainations about it are as follows:1)Xu Xiake mistook the mileage of the Bomeng and Duiyong mountains for that of the North Panjiang River and the south Panijaug River.2)There are something to be left out seriously in"The Investigation on the Panjiang River" 3)The diary on 24 Sept.1637 annotated by others instead of Xu Xiake himself.Spreading it from place to pa place,the writer’s name disappeared.Or the writer did not sign at the very beginning.4)The diary on 24 Sept.1637 was written by Xu Xiake himself,while "The Investigation on the Panjiang River" was writtern by somebody else in Xu’s name.