An automatic inducing method based on road flow detection includes the following steps of firstly, setting a flow division threshold value and a flow division ratio value; secondly, scanning each road section in a city according to a scanning sequence, stating a next round of scanning after one round of traversal scanning is completed, and when a certain road section is scanned, conducting following judgment and corresponding operation, namely, calculating the lane average flow L of the road section, the left lane average flow L of a left adjacent road section and the right lane average flow L of a right adjacent road section, issuing inducing information at a starting crossing of the road section and guiding vehicles to flow to the adjacent road sections when the L of the road section reaches the flow division threshold value and the ratio of the lane average flow of each adjacent road section to the lane average flow of the road section is smaller than the flow division ratio value, and stopping issuing corresponding inducing information when the inducing information has been issued and the lane average flow of the road section is smaller than the lane average flow of each adjacent road section. The invention further provides an automatic inducing system. The automatic inducing method and system are good in accuracy, good in instantaneity and high in urban road use ratio.