The chemical composition of the essential oil isolated by hydrodistillation from the flower part of Dracocephalum integrifolium Bunge was analyzed by GC/MS, and the activity of phytotoxicity was tested. Thirty three compounds were identified, representing 95.97% of total oil, which was found to be rich in monoterpene hydrocarbons (29.21%)，oxygenated monoterpenes (17.27%)，sesquiterpene hydrocarbons (23.84%) and oxygenated sesquiterpene (25.65%). The main constituents of the oil were eucalyptol (15.55%), α-bisabolol (10.29%), nerolidol, cis-(+) - (8.81%), β-Pinene (8.25%), (E)-β-ocimene (7.44%) and α-thujene (5.45%). The essential oil completely inhibited seed germina-tion of Amaranthus retroflexus and Poa annua at 2 μl/ml, meanwhile it exhibited weak activity on Echinochloa crusgalli. In general, the oil possessed promotive activity at low concentration and in-hibitory activity at high concentration. This is the first report on the chemical constituents as well as the phytotoxic activity of the essential oil of D. integrifolium flowers.