The traditional calculation methods of mortar thickness without considering creep of the bridge caused by the mortar thickness, affects the safety and quality of the bridge. This paper proposes a mortar thickness calculation method of bonding layer in large-scale bridge construction based on Kalman filtering. The method uses the mortar creep impact indicators system, selects the creep test data as sample, and analyzes its sensitivity to the thickness to get the intensity of factors affecting mortar creep. It also filters the interface of amount of cement, aggregate content, water-cement ratio and components, and effectively computes the thickness which reduces the cost while improving the quality of bridge construction.