Abstract: This research aims to establish a method to predict the dome thickness of composite pressure vessels. According to the dome shape of cured composite pressure vessels, a cubic spline function was presented to predict the dome thickness based on the volume of all fiber tows being constant. Using this method, the dome thickness of an arbitrary composite pressure vessel with different geometrical parameters and process parameters was forecasted. The predictive results were compared with the traditional methods and actual measured thickness. The results show that dome thickness obtained from the cubic spline function could reflect actual measured thickness better than the other methods and it could provide more accurate thickness parameters for the finite element modeling.