The invention discloses a diesel engine crankshaft which comprises two crank arms which are parallelly arranged, wherein the two crank arms are connected by virtue of a crank pin, the crank pin is arranged on one ends of the crank arms, the lateral surfaces of the two crank arms are respectively provided with a main shaft, the two main shafts are coaxially arranged, and the main shaft and a crank pin are eccentrically arranged; and the other ends, opposite to the crank pin, of the two crank arms are molded into a counterbalance block, the opposite inner sides of the two crank arms are respectively provided with a discharge spout, each discharge spout comprises a first part which is extended from the axis of the main shaft to the crank pin and a second part which is extended from the axis of the main shaft to the counterbalance block, the first part is a rectangular slot the surface and end wall of which are in an arc chamfer shape, the second part is a rectangular slot the end wall of which is a flat slope surface, and the distance C from the axis of the main shaft to the end wall of the discharge spout is greater than the groove depth E. The balance property of the complete machine is improved by the crankshaft, the transitional fillet stress peak value of a right crankshaft pin and a left crankshaft pin is reduced by 11%, the reliability of the crankshaft is improved.