Insecticidal crystal proteins of Bacillus thuringiensis (Bt) with high specificity have effect on the target pests but are harmless to natural enemies and other insects. The transgenic Bt plants and Bt insecticides are the most widely used biological control technique. This paper detailedly reviewed the discovery, classification, structure and function of Bt. The insecticidal mechanism of Bt, resistance mechanism of pest insect to Bt and receptor proteins of Bt from insects with relation to resistance were also given, and the insect resistance management strategies and prospects of Bt crops were proposed.