For a V-type six-cylinder supercharged diesel engine, the transient engine speed and the pressure in each cylinder were measured under different engine speeds and loads. The correlation between the fluctuations of transient engine speed and the combustion nonuniformity of the six cylinders were analyzed. The results indicated that a wave peak of transient engine speed emerges at the point between the two peaks of cylinder pressure of two adjacent fired cylinders. And, the more the output of positive work is in one cylinder, the larger the subsequent peak value of fluctuant engine speed is. When the mean engine speed is constant, the higher the load is, the larger the fluctuation ratio of engine speed is. However, when the load is same, the fluctuation ratio is independent to the mean engine speed.