Recently there has been an increase of clinical cases of osteoporosis due to an increase in the ageing population. As an established diagnostic tool for osteoporosis, dual-energy x-ray absorptiometry (DEXA) is widely used due to its high accuracy, precision and image quality. In recent years, a new type of silicon-based photomultipliers, SiPMs, has been developed which has high potential to be used in photon counting DEXA detectors for its compact size and reliable performance. In this work, we designed a DEXA test platform with a SiPM and evaluated its performance using various bone density imaging parameters. The experimental DEXA platform is constructed with a fan-beam geometry consisting of an x-ray source from Spellman and a self-developed scanning motion control system. We studied the performance characteristics of a 64-channel YSO/SiPM array detector and compared them with a cadmium zinc telluride (CZT) detector. The maximum-likelihood (ML) estimation method was used to optimize the surface fitting algorithm to achieve high material decomposition accuracy. The results show the average error of the YSO/SiPM detector is 1.24% for PMMA and 1.72% for Al. We conclude the YSO/SiPM detector can achieve material decomposition accuracy close to CZT detector and it has the potential in DEXA imaging with good imaging performance characteristics at low cost.