For the need of multi-channel simultaneous sampling in the modeling and identification of power system, a portable data acquisition system is introduced. It can sample multi-channel data simultaneously, and also have a mass data storage. The system is composed of data acquisition card and PC processing software. The C8051F410 MCU is the core of the data acquisition unit card. It not only provides multi-channel synchronous sampling, large storage capacity, easy to carry and low cost, but also can run offline, and bidirectional interaction with PC software. The data processing software is programmed by Visual Basic6.0. Its main function is sending sample orders and the sample data processing. It can store and process the sample data, also it can set the sampling parameters of the card. Through actual verification, the system is easy to use and meets the precision of requirement.