With the dispersion relation of the ion temperature gradient mode( ITG) and the trapped electron mode( TEM) derived from the Weiland model,where the two fluid equa-tions with the collision term are used,the effects of the normalized temperature gradient, the normalized density gradient and the normalized radial coordiante on the growth rates of these two modes are analyzed. The computation results indicate that the ion temperature gradient modes are stablized by the plasma density gradient and the traped electron mode is destabilized by the density gradient. The growth rate of both modes incre...