Dissolved oxygen (DO) is an essential indicator in chemical, biological and biochemical processes and needs to be rapidly measured in many cases. In this work, a rapid, sensitive and simple electrochemical method, first derivative linear sweep voltammetry (FD-LSV), was established for the determination of DO. The peak height of FD-LSV was found to be influenced by scan rate and microelectrode surface area. An empirical formula was proposed to describe the relationship between the FD-LSV peak height and the influencing factors. Compared with other electrochemical methods for DO determination, the FD-LSV method needed lesser time and was more accurate. This method was successfully applied for the determination of the DO levels of various environmental water samples.