Abstract: With the development of offshore engineering, jack-ups have moved into deeper and harsher environment, hence increasing need to understand the behaviors of jack-ups and to develop more reliable analysis techniques. In order to improve the prediction accuracy, based on the characteristics of the spudcan penetration in sand, the spherical cavity expansion theory is used to analyze the penetration resistance of spudcan under no backflow condition. At the same time, this method is also used to present cone tip resistance of CPTU. According to the analytical solutions, the relationship between spudcan penetration resistance and cone resistance of CPTU is established. In order to verify the reliability of the relationship, the spudcan penetration depths of six jack-ups in South China Sea are predicted by using the traditional method and the proposed method respectively. The predicted results are compared with the measured data. It is shown that the results by the proposed method are in better agreement with the measured data than those by the traditional method commonly used today.