This paper aims to develop a sequential three-phase power flow program with three-phase ZBus distribution factor(TZBD) for power flow calculation. First, using monthly energy consumption of customers in a customer information system (CIS) and typical daily load pattern of customer classes, the quarter hourly loading profiles of distribution transformers were derived. The derived daily load curves are the loading database for the sequential three-phase power flow program. Next, the implicit Z-Bus Gauss method as well as the line flow and bus voltage sensitivity factors are integrated together to develop the sequential three-phase power flow program. Finally, the IEEE 4 Node Test Feeder is employed as sample systems to be analyzed the daily operation profiles, include the daily line flows and voltage profiles curves by the developed sequential three-phase power flow program. This study is helpful for modern electrical power distribution operations, and distribution automation.