Present work deals with the study of queueing system by maximizing the generalized entropy subject to some constraints. Generalized entropy is simply applied to obtain the widest probabilistic model subject only to constraints expressed by mean value as the mean arrival rate, the mean service rate, or the mean number of customers in the system. Some interesting theorems in queueing theory dealing with maximum entropy condition have been proved when the queueing system is in a steady state condition and if the requirements of a birth and death stochastic process are satisfied. Also, some results obtained by Guiasu and Jain can be derived as particular case of the present work.