Abstract: Two-dimensional (2D) transition metal dichalcogenide (TMDC) alloys and heterostructures have a great potential in next generation optoelectronic devices due to their unique optoelectronic properties. However, controllable synthesis of 2D TMDC remains a major challenge. Taking the heterostructure and alloy of WS2and MoS2as examples, we introduce various contents of low melting point Tellurium powder to effectively reduce the growth temperature of WS2, and then regulate the nucleation and growth rate of WS2. Then the WS2/MoS2vertical heterostructure and the Mo1-xWxS2alloy could be controllably synthesized by a one-step chemical vapor deposition method. Raman and photoluminescence spectra and mapping show that the prepared WS2/MoS2vertical heterostructure is formed by superimposing monolayer WS2and monolayer MoS2. The content of W (x) is 0.83 in the as-synthesized Mo1-xWxS2alloy. This work provides a simple and effective method for two-dimensional TMDC heterostructures and alloys.