In this paper, the effect of long wall assumption (LWAM) on the analyses result of axially symmetric cylindrical wall is investigated. For that reason, key parameters that effect on the assumption is changed around the limit of validity of the assumption. The results obtained from the analyses are compared with results of the Superposition Method (SPM) which is considered one of the easy and powerful methods used in the analyses of the cylindrical walls. In order to obtain the exact analyses results, the internal forces were calculated for triangle distributed load that used in numerical examples and the expression were employed during the analyses of SPM. According to the analyses results, in some cases significant errors can occur in the results of the methods.