A flexible measurement technique is proposed in this paper to measure the mass and center of gravity of large-sized objects. Based on primary mechanical principles, this technique derives measurement results by fusing data from two different systems. During a test, a high-precision coordinate meter is used to measure reference points in these two systems and designated points in the test object. The measurement results obtained from the two systems are then merged in a single coordinate frame. The proposed flexible measurement technique may be applied to test objects of varying lengths, and meanwhile does not require strict control over the distance between the two measurement systems and that between the test object and the systems. This paper describes basic measurement principles of this technique as well as the data fusion method and transition matrix solving method concerned, which are followed by experiment-based verifications. The test results reveal a mass measurement accuracy of 0.05% and a center of gravity measurement error of within  ±1 mm, both meeting high-precision requirements for measuring mass and center of gravity of large-sized objects.