The present disclosure provides a visual analytical method for a network system structure and a network communication mode including following steps: pre-processing network traffic flow log data; dividing and analyzing network nodes by utilizing a visualization technology according to the pre-processed data, and combining a user interaction to determine server nodes and client nodes in the network nodes; performing a visual analysis on traffic flow and an access situation of the server nodes to determine a server function category according to the determined server nodes; and presenting and analyzing the network communication mode through the visualization technology according to the determined server nodes, the client nodes and the server function category. The present disclosure further provides a visual analytical system for the network system structure and the network communication mode.