Magnetic two-dimensional materials have attracted immense consideration as spintronic devices. However, design and synthesis of the magnetic two-dimensional MoS2 crystals with more controllable electronic structure and better conductivity are still great challenges. Here, we make a breakthrough to synthesize the MoS2:Dy sheets with robust adjustable room-temperature ferromagnetic properties by a gas-liquid chemical deposition method. The as-synthesized samples are characterized by XRD, Raman, TEM, HRTEM and XPS. Furthermore, the magnetic properties of the samples are also investigated by VSM and Squid. The maximum observed saturation magnetization is 0.023 emu/g. The origin of ferromagnetism in the samples is investigated by using the first-principles calculations based on the density functional theory. The ferromagnetism is mainly related to the exchange interactions among the S 3p, Mo 4d and Dy 5d orbits. The results indicate that the transformation of the localized charges can effectively engineer and manipulate the magnetic properties of 2D materials, making MoS2 a potential candidate for spintronics and electronic applications and providing a new perspective on other 2D layered materials in spintronics application.