Abstract: Seismic array is a seismic observation system originally built for detecting underground nuclear explosions. Nowadays, seismic array has been developed into the study of the Earth's interior structure, and then greatly promotes the development of seismology. This article gives an introduction to the various seismic array techniques such as beam-forming method, slant stacking techniques,Nth root slant stack process, frequency-wave number analysis and phase-weighted stack, and discusses the advantages and disadvantages of the techniques. As to the detecting of weak but coherent arrivals, phase-weighted stack and its applications will be discussed. It turned out to be a great improvement of the signal-to-noise ratio (SNR) in different degree. These array data of high quality make it possible to research the fine-scale structure tomography of Earth's interior.