The technics for predicting thermal cycle of a quenching by using the finite element method have been studied by comparing theoretical values with numerical analysis results. The basic equation of a minimum element length for cylinder thermal cycle was proposed, which was able to calculate from informations such as an initial temperature, a radius of cylinder, a heat transfer coefficient and the aimed temperature change at the cylinder surface. The minimum time increment for guaranteeing accuracy was given corresponding to the minimum element length. It was shown that the minimum element length for pipe thermal cycle was replaced by that of cylinder. Temperature distribution in cylinder during quenching process can be sufficiently predicted by the finite element method with the above, mentioned minimum element length and the minimum time increment.