While China's targeted poverty alleviation has achieved great success, it also faces the problem of lacking long-term efficiency. The "dual character" of government power to poverty alleviation, the "positive externalities" of poverty alleviation, and the "weakness" of the poor are important reasons for the problem of lacking long-term efficiency. As modern and standardized poverty governance mechanism, governing poverty by law can resolve the "dual character" of government power to poverty alleviation, relieve the "positive externalities" of poverty alleviation, and transform the "weakness" of the poor, thus can effectively realize the sustainable development of targeted poverty alleviation. However, governing poverty by law also faces the problems of lack of legal supply of targeted poverty alleviation, lag of implementation system for operation of pertinent government power, low efficiency of incentive mechanism for social participating poverty alleviation, and the deficiency of rights to livelihood for the poor. Therefore, this paper suggests:perfecting the legal system of targeted poverty alleviation, optimizing the rule of law implementation system for the operation of pertinent government power, improving the legal incentive mechanism for the participation of multi-subject, and establishing the system of rights to livelihood for the poor.