The dissolved oxygen is one of important factors to evaluate the quality of water. Currently, various aeration and oxygenation devices have been developed for increasing its oxygen concentrations in water. However, the operations of those devices usually depend on the human operation with experience. In this study, we have developed a PC-based virtual instrument (VI) system using LabVIEW, which can monitor and control the dissolved oxygen (DO) concentration automatically. Via the Internet, a nearby PC (server) of the system can collect real-time DO data from different multi-locations and transmit it to another remote PC (client) for online analysis, monitoring and control. The DO history from remote locations can be also recorded and tracked in the data base. Further, the proposed system has been successfully tested using the model aquafarm, showing an effective and reliable performance. The experimental results showed that the proposed system is capable of reducing the business costs in term of automation mechanism, high efficiency and low electricity consumption.