The invention relates to a method for straightening a crankshaft, in particular to a method for straightening a diesel engine crankshaft at normal temperature. The method comprises the following steps: measuring the position, the direction and the value of tripping tolerance of the crankshaft, and marking; on a platform, placing the deformed crankshaft on V-shaped iron, the span of which is not less than that of the shaft neck of the third gear crankshaft; turning the bending point of the crankshaft to right above, pressing the high point of the crankshaft to straighten the crankshaft, and adjusting a dial test meter to the pressure point; pressurizing the crankshaft, using the dial test meter to measure out the back value of the crankshaft pressure, which is determined by the deformation amount of the crankshaft, and keeping for 10-15 days after one time of back pressure. When the deformation amount of the crankshaft Delta d is larger than 0.40mm, the pressurization straightening is carried out in 2-3 times or more times; during forcible straightening, the one-time straightening force cannot be too large; instead, the strengthening force can be increased gradually; when the deformation amount is large, the straightening should be carried out in several times; the one-time pressure back value is not allowed to be negative. Compared with the prior methods, the method is simple and practical, and can improve the crankshaft overhaul efficiency.