To tackle the inaccuracy problem of the tension caused by complicated boundary conditions of cables, the ambient vibration method based on estimated effective vibration length was proposed. The results of a series of analyses and experiments validate that the proposed method can estimate cable tension with high accuracy. This paper further extends the cable-tension estimation methodology, particularly focusing on its application to the case of tension members with non-uniform cross section. In order to manipulate the problem induced by more than one cross section in tension members, the effective vibration length used to calculate cable tension in original solving algorithm is replaced with half wavelength. The feasibility and accuracy of the proposed concept is verified with demonstrative numerical examples and laboratory mock-up test. There are three cases considered in the numerical analysis. Two of them are the tension members composed of two different cross sections. The third one is the uniform tension member with lumped mass near the end. To construct the measured tension member in mock-up test, 8.444 m long and 12.7 mm in diameter, was stressed and then combined with 2 m long unstressed strand. Overall speaking, the results demonstrate the outstanding accuracy of the proposed method in determining the tension of members with non-uniform cross section.