In the real world, the time interval of each customer into a store and the quantities of products bought by customers can be seen as a random variable. Under this circumstance, it is a very important issue for retailer to control the inventory and ordering strategies to make the best profit. However, the expired date and the demand of products are different. Therefore, the main purpose of this study is to find the optimal ordering quantity under the consideration for different parameters. This research is developed from the concept of time interval and random product’s demand. Through the data collection of practical observation and the characteristics of perishable goods, the researcher can inference the demand distribution of perishable goods by applying statistical theory. Thus, the mathematical models can be developed to find out the optimal ordering quantity to maximize the total expected profit and then sensitivity analysis is taken for system parameters. Finally, a numerical example is demonstrated and the researcher derived four specific conclusions for further studies and practical application.