Abstract: It is proved from the equations of errors that the isolines of errors in wind measurement by a triple Dopplerradar systemare concentric circles and the more radius is,the more erroris.The position of circular centre and size of radius with given errorare related to relative positions among three radars and measuring velocity precisions of each radar.If the measuring velocity precisions are the same for three doppl erradars,the optimum arrangement of the three radars is a equilateral triangle.The length (l) ofone side of equilateral triangle is related to measuring velocity precisions and errorr equirement and maximal distance (L) of radar detection.if precision=1 m/s and error ≤2 m/s,then l=0.55L.