The cell's sense direction is closely related with the proteins that contain PH (pleckstrin homology) domain. PH domain has been found in about 60 proteins, many of which could activate the sequent events of signal transduction via combining with the related binding sites on the surface of chematactic cells. The characteristics of this combining are: a.rapid and transient; b.It is only related to the concentration gradient of surroundings outside cells, which is the base of spatial model; c.The distribution of the binding sites on the cell membrane changes when the researchers altered the position of the chemoattractant. This is the base of temporal model. To deeply investigate the effects of all kinds of proteins which contain PH domain on cell's sense of direction will greatly promote the research of this field, and hence, has great theoretical significance.