The simple analysis and curve fitting based on the diurnal maximum,minimum and diurnal range of soil temperature at different depth at field experimental site in typical coastal region of north Jiangsu province during fourteen months,showed that the variation of the diurnal maximum and minimum soil temperature approximate to sine curve in all depths,and all the coefficient of multiple determinations(R2) were equal to or higher than 0.767.As soil depth increased,diurnal maximum and minimum of soil temperature fluctuated more and more weakly,and diurnal range was near to zero.