A Lumped Parameter (LP) model of Torsional Vibration (TV) in engine crankshaft system is established, and a detailed procedure for determining the inertias, torsional stiffness and damping coefficients of the LP model is presented. The proposed model is then used to calculate the natural frequencies of crankshaft and the TV of cranknose with cylinder loads. A test is carried out to obtain the TV of an engine crankshaft, and the experiment data is compared with the calculated results. The comparison shows that the calculated natural frequencies o f crankshaft and TV amplitude of cranknose agree well with the measured values, which validates the proposed model and the method for determining parameters of the LP model. Thus, the modeling method of crankshaft system and the procedure of determining parameters of the model presented in this paper can be used for the design and calculation of TV Absorber (TVA).