This paper presents the studies of the dependence of soft X-ray emission on atomic-number and laser intensities by using a new diagnostic tool, pinhole transmission grating spectrograph (PTGS). Plasma X-ray spectra of various elements from Z = 6(C) to Z = 79(Au) produced by a laser beam with an average power density 5×l014W/cm2 reveal the strong dependence of X-ray emission on atomic number Z. Comparative experiments of Al or Au plasma X-ray emis-sion under both spot and line focused laser illumination show that changes of the laser intensity have more remarkable influence on low Z plasma X-ray emission than that on high Z.