Controlled stacking of different two-dimensional (2D) atomic layers will greatly expand the family of 2D materials and broaden their applications. A novel approach for synthesizing MoS2/WS2 heterostructures by chemical vapor deposition has been developed. The successful synthesis of pristine MoS2/WS2 heterostructures is attributed to using core-shell WO3-x/MoO3-x nanowires as a precursor, which naturally ensures the sequential growth of MoS2 and WS2. The obtained heterostructures exhibited high crystallinity, strong interlayer interaction, and high mobility, suggesting their promising applications in nanoelectronics. The stacking orientations of the two layers were also explored from both experimental and theoretical aspects. It is elucidated that the rational design of precursors can accurately control the growth of high-quality 2D heterostructures. Moreover, this simple approach opens up a new way for creating various novel 2D heterostructures by using a large variety of heteronanomaterials as precursors. ; Institute of Textiles and Clothing