The invention relates to the technical field of building equipment, in particular to a three-point positioning measuring, setting and placing device and method. The three-point positioning measuring, setting and placing device comprises a first rod piece, a second rod piece, a third rod piece and a placing seal; the
shortest distance between the point position of a to-be-measured setting point and the upper, lower, left and right edges of the
building unit is a first distance a, the second
shortest distance between the point position of the to-be-measured setting point and the upper, lower, left and right edges of the
building unit is b, and the second edge is perpendicular to the first edge. A point position of a setting point to be measured and a certain point of the first edge are connected to form an
oblique line, an included
angle alpha between the
oblique line and the first rod piece is 30-60 degrees, the length of the
oblique line is c, the length of the first rod piece is a, the length of the second rod piece is b, an included
angle alpha between the third rod piece and the first rod piece is alpha, and the length of the third rod piece is c. The device provided by the invention has the advantages of high speed of measuring and setting points, small error and capability of reducing material waste.