Abstract: To solve the problem that we can’t take the right interference suppression method to improve the performance of direct sequence spread spectrum(DSSS) communication system because of the unknown interference types, an algorithm to automatically recognize interferences is proposed. First, the mathematical models of 8 important interferences in DSSS communication system are made; Then, the features of interferences from time domain, frequency domain and time-frequency domain are extracted; And finally, a fifth-order automatic interference recognizer based on decision tree support vector machine is constructed, and the automatic recognition of the interferences is realized. Simulation results demonstrate that the proposed algorithm provides a very high recognition rate when ISR isn’t lower than 9dB.