Atomically thin two-dimensional (2D) materials and their heterostructures exhibit highly unusual behaviors. In this work, the isoelectronic doping of W into MoSe2 monolayer crystals is realized by a chemical vapor deposition (CVD) method. We find that the electronic properties of atomically thin 2D MoSe2 crystal can be modified significantly thorough controlled doping, which lead to the p-type semiconducting properties after doping from n-type of MoSe2.