The main propose of this article is to establish optimal ordering strategy for single period multiple perishable products under stochastic demand. Because the customer arrival time is Uncertainty, so we regard the product's sales quantity as a random variable, and then extend traditional newsboy problem. For practical applications, we divided sales period into weekday and holiday two conditions to explore, and construct multi-product newsboy problem model with space and budget constraints. However, an EM algorithm is provided in this paper that can maximize the total expected profit under space and budget constraints. Then, sensitive analysis is also taken to find out the influence of each parameter for total expected profit and ordering quantity. Then a numerical example is taken to illustrate the model and provide some insights. Finally six conclusions are drawn for practical applications and future studies.