Abstract： The crystal of dimethyl sulphoxide complex of europium Eu (NO3)3·4DMSO belongs to the monoclinic system. The space group is C2/c-C62h. The cnystal parameters are a = 14.806 (9)?, b = 10.948 (3)?, c = 15.335 (4)? and β= 108.07 (7) °. Four molecules are contained in a unit cell, z = 4. The diffraction data have been collected by using PW-1100 four-circle diffractometer, the total number of independent diffractions amounts to 2270. The structure was solved by heavy-atom method, and structure parameters have been refined by means of full-matrix and block-diagonal least square method, R = 0.069. The europium ion in this structure is found to be coordinated by ten oxygen atoms. The distances between the europium and the coordinating oxygens are Eu-ODMSO=2.38?, Eu-O(NO3)=2.61?.