Abstract: The optimization problem of the supermarket cash register service system was transformed into the M/M/S/∞ Poisson input-index service queuing model, which solved the problems of the number of customers and the arrival time. Based on histogram and Poisson distribution probability density curve, negative index probability density curve distribution for preliminary comparison, the distribution form of data was determined, the parameters were estimated by maximum likelihood method, and then they were tested with χ²-test method, the service system analyzed and optimized with the queuing theory. Through the optimization of the cashier system, customer satisfaction and service quality are improved.