[Objectives] In this work, the influence of initial heeling angle on the roll response of a ship in random beam seas is studied. [Methods] Specifically, the path integration method is applied to solve the Fokker-Planck equation, which governs the probability properties of the stochastic differential equation for the roll motion. Then, probability distributions of the roll response can be obtained. [Results] The path integration method has the advantages of high accuracy and high efficiency, this method is able to accurately predict the roll responses of ships with or without initial heeling angle. The results show that the initial heeling angle has limited influence on the roll response spectrum, however, the probability density function of the roll response as well as the distribution of the extreme roll response could be significantly influenced by the heeling angle. As a result, the safety and stability of ship would be dramatically deteriorated. [Conclusions] The path integration method could be an effective method to study the characteristics of ship roll motion under random waves, the initial heeling angle has a significant influence on the stochastic roll response.