A goggle and a strap assembly method thereof are provided. The goggle includes an eyeglass, a frame and at least one strap. The frame receives and secures the eyeglass therein and is bilaterally provided with a pair of engaging portions each having a through hole. The strap has at least one connecting portion and is passed through the through hole of a corresponding one of the engaging portions of the frame. The connecting portion of the strap is provided with a resisting portion which makes the connecting portion slightly larger than an opening of each of the through holes, so that the strap which is passed through the through hole of a corresponding one of the engaging portions can be securely attached to the frame.