In this paper we proposes a new method to detect a slanted ellipse using Hough transform with 5 parameters effectively. The procedure is as follows: First, a pair of arcs are detected as a part of the slanted ellipse using a circle detecting Hough transform with 3 parameters; the central point (xc,yc) and the slanted angle 9 can be obtained. Second, the slanted ellipse is transformed into a normal ellipse whose central point is (0,O) and slanted angle is zero degree. Two parameters of a normal ellipse, the major axis and the minor axis (a and b) can easily be obtained by 2 parameters Hough transform. Thus, the slanted ellipse can be detected with less memory and less data processing.