To meet the power supply integrated protection functional requirements and hard real-time requirement, a kind of integrated protector to power supply is designed, using Cotex-M3 chip MCU and source library function and based on μC/OS-III real-time operating system. According to the system requirements, the protective functions are divided into 10 tasks, including data process task, protection task, GUI task, etc. With the task communication and synchronization realized by kernel objects of μC/OS-III, such as task semaphore, task message queue and event flag group, the tasks are managed based on task priority, so that the system runs real-timely. And it is indicated that the software design based on μC/OS-III can realize stably real-time running of the multitask protective system by monitoring experiment. Through the correct set to detective function of μC/OS-III system task, the system state and the operational details of software are detected, making for later software upgrade. This work is supported by National Natural Science Foundation of China (No. 61340015) and Natural Science Research Project of Education Department of Henan Province (No. 2010A470003 and No. 2009B470003).