Fringe projection profilometry (FPP) has been widely used for three-dimensional shape measurement because of its simple hardware and high measurement accuracy. However, the use of most FPP systems to measure complex surfaces such as stepped height objects can result in severe occlusion and shadow. To alleviate this problem, a coaxial measurement method based on dual biprisms is presented in this paper. The system is low-cost and easy to implement, and does not require the introduction of mechanical moving parts. Only dual biprisms are introduced into the coaxial system to provide the geometric constraints required for reconstruction. Experimental results on the reconstruction of a surface with significant height changes demonstrate that the proposed method can achieve shadow-free measurements.