The Schrodinger's equation method is used to investigate the squeezing phenomenon of the electromagnetic field in the case of a three-level cascade atom interacting with single-mode cavity field. The effects of the stimulating strength and the coupling constants on the squeezing phenomenon are discussed. Furthermore, the roles played by the saturation effect and the two-photon process, and the relation between the 1st order coherence and the squeezing effects of the field are revealed.