The invention provides a tree target volume real-time measuring method based on a two-dimension laser scanner. The method is characterized by obtaining tree laser data through a vehicle-mounted two-dimension laser scanning sensor, obtaining crown center distance through trunk identification, and calculating discretized crown volume corresponding to each shower nozzle with the measured crown outer edge distance and vehicle speed being combined. The tree center position is obtained through trunk identification, and thus crown depth is calculated; with the carrier vehicle speed being combined, the crown volume can be obtained, and a variable-rate spraying-oriented spray prescription map is generated; and the method is suitable for the cases of irregular tree cultivation. The tree crown volume measuring method is fast in processing speed, good in real-time performance, and can meet the real-time tree target variable-rate spraying requirements.