Abstract: A method of joint frequency and DOA estimation based on spatio-temporal co-prime sampling is proposed for muti-narrowband signal which spreads over a wide spectrum. In the space domain, a co-prime array is adopted. Following each array element is a co-prime sampler. A two-dimensional difference coarray is produced by the construction of spatio-temporal covariance matrix. This method can not only achieve efficient estimation of frequency and DOA, but also gives much higher degrees-of-freedom(DOFs) than traditional methods. In addition, the optimum selection criterion of co-prime parameters is also discussed. Simulation results demonstrate the correctness and effectiveness of the novel approach.