Abstract: Statistical analysis of the X-ray prop erties of 247 quasars in the 0.5-4.5 keVband observed from the Einstein Satellite,are carried out in this paper which is one of a series of papers devoting to the study of X-ray quasars and active galactic nuclei.The following main results are found:1.Among all the 1619 known quasars of various apparent magnitudes and red-shifts (or distances),those detected as X-ray sources are of nearly equal percentages.2.There exists a weak correlation between the optical radiation and the X-ray radiation.The correlation coefficients in some cases are shown in Table 1,which shows clearly that the radio emission with frequencies higher than 2.5 GHz correlates strongly with X-ray radiation,implying that the emitting regions in these three bands (optical,high frequency radio anl X-ray bands) are close to one another in order and that their emitting mechanisms are similar.3.There is a strongly correlation between the radio R_EW of equivalent widths of the emission lines H_β and [OIII],and the X-ray luminosity L_x (0.5-4.5 keV) for type I Seyfert galaxies (Fig.10),whose properties are similar to those of radio-quiet quasars.We propose this correlation [equation (5.2)] as a new X-ray luminosity indicator for type I Seyfert galaxies.4.Neither the color index U-Bnor B Vcorrelates with X-ray radiation,but U-Bcorrelates with B-Vweakly.Acknowledgement: One of the authors (H.S.Yang) thanks Dr.G.Burbidge,Director of Kitt Peak National Observatory (Tucson,Arizona,U.S.A.),for many helpful discussions during his stay at KPNOwhere part of this work was done.Yang thanks also Mr.J.Wagner for help in using computer.