Deflection is a key index to reflect the bearing capacity and the operation situation of bridges. As the existing measurements methods have their limitations, this paper tries to introduce a new method using suspension cable to measure the deflection of bridges. This method sets the supports for dial meters by erecting main cables and sets up longitudinal measuring points on the bridge deck. The existing of counterweights and limit bars avoids the horizontal disturbance of the structure and keeps the stability. The tools used in this method are light and convenient to adapt the complex conditions. This method has been successfully used in the bridge inspection and has obtained the precise data that reflects the change of deflection of the bridge.