This research summarized the possibility of prediction of the cylinderpressure (combustion pressure) of internal combustion engine by measuring thevibration amplitude at the housing of the main bearing of crankshaft.A mathematical model was developed using the Transfer Matrix Method toanalyze the crankshaft vibration. The journal bearings were modeled as springsand dampers in the direction of main system coordinates. The bearings wereunder dynamic load conditions. This was achieved by sampling the crankshaft tomulti-supported beam using the Equation of Three Moments Theory. A relationbetween the reactions were found at main bearings and the applied forces on thecrankshaft as a result of pressure and the effect of both reciprocating androtating motion .A computer program in Fortran language was developed for each citedsample.The study depends on experimental results previously measured on (Zetor MType),four stroke, 4-cylinders diesel engine under motoring condition usingspecial prepared computer program. The resulting amplitude of vibration at localposition were compared with the experimental amplitude also the cylinderpressure were corrected until a convergence criterion is reached between thetheoretical and the experimental amplitudes. The instantaneous cylinder pressurewill be predicted, two samples of data were taken for the amplitude of vibrationat two rotational speeds.The results show good agreement with those obtained experimentally. Alsothe rotational speed was deduced by the use of practical measurement ofvibration amplitude and cylinder pressure for two rotational speeds using thesame program with simple change and showed good agreement betweenpractical and theoretical results.