Abstract: A new method of standardizing sulfur dioxide standard solution has been presented, in which iodine that is derived from the reaction of KIO₃with excess KI istitrated directly.Comparing with standard methods, the new way does not need to prepare and standardize the unstable Na₂S₂O₃solution and use
volatile I₂. As a result, the analytical time is shortened and the cost is reduced. The reaction condition is easy to reach and the method has high accuracy (CV≈0.082%, RE<±0.4%).It is a method that is worth recommending.

Key words: sulfur dioxide, sodium sulfite, environmental monitoring, standardization