Abstract:The feeding habit, quantity of food-taking of Locusta migratoria tibetensis Chen and the output loss of the highland barley and pasture grass by the pest were studied in this paper, and then the action threshold was worked out. The results showed that 1st-2nd instar nymphs of locust fed mainly on pasture grass, after the 3rd instar, Locusta migratoria tibetensis fed mainly on highland barley and winter wheat. The locusts could obtain the necessary nutrition on pasture grass (subalpine meadow), highland barley and winter wheat for its growth and development in its life history, but it couldn’t complete its life history when it fed on Hippophae rhamnoides and Chinese cabbage. The quantity of food-taking of the 1st-3th instars nymphs was very low, but the quantity of food-taking of the 5th instar nymph and the adults was huge. The action threshold for this pest feeding on highland barley was 3.01 nymphs per square meter, and the action threshold on pasture grass was 4.44 nymphs per square meter.