In this paper, the incompatible displacement functions are constructed which possess completeness in Cartesian coordinates. A pair plane quadrilateral isoparametric incompatible elements are given. 本文利用直角坐标下函数的完备性来建立等参坐标下的非协调位移函数,给出了一对在直角坐标下二次完备的四边形平面等参非协调元。