Generating valley polarization is the key process in valleytronics. In this work, the valley polarization properties of WSSe induced by transition-metal (TM) doping or adsorption are investigated through first principles calculations. Both the doping and adsorption of TM atoms can induce valley polarization after considering spin orbit coupling in the WSSe system. Different impurity energy levels will be introduced by the TM doping or adsorption, and the hybridization between these impurity energy levels and the highest valence band of WSSe will influence the valley polarization properties. Big valley polarization can be obtained in the cases of V doping or Cr adsorption on the Se-surface in WSSe. Valley polarization can be induced and controlled by TM doping or adsorption in WSSe, which contributes to anomalous valley Hall effects.