In this paper, the basic model of main cable slip between saddles is established. Three methods to assess the safety of saddle sliding on middle tower of the Taizhou Bridge are presented based on this model. The first assessment method is deterministic, which is based on live load model of design codes. Several design codes models are used, and assessment results are compared. In the second method, the uncertainty of traffic load is considered in a more accurate way. Random traffic flow simulation model is developed to simulate real traffic situation on the bridge. Extreme value of unbalance force is obtained by extrapolation methods based on Rice formula. The last assessment method is probabilistic based method.The probabilistic model of load effect and structure resistance is established, and reliability index of anti-sliding safety is calculated. All three assessment results indicate that the middle tower saddle of the Taizhou Yangtze River Bridge is safe and reliable.