Abstract: The monitoring data of dock cofferdam is very important in the construction of dock. However, some incorrect factors led to the monitoring data does not match the actual situation. while the abnormal value can not be intuitive removed, thus it has a great impact on dock cofferdam construction safety monitoring, So it must be judged and handled. This article introduced 3σ, Grubbs and Dixon methods to handle the Gross Error, and applied them to the concrete dock cofferdam construction safety monitoring. The results showed that these methods which provide help to the dock cofferdam construction. They can quickly, easily and effectively handle the abnormal value in some degree.