Usually three to five years. Because the doctor of law must complete a certain number of designated courses during his study, after passing the doctoral qualification examination, he must also complete the periodical papers and dissertations required for the doctoral stage, and he must pass the thesis defense to get the diploma, so he needs to study for 3-5 years. Doctor of law is a doctor's degree in the higher education system, which belongs to the final degree. Doctoral students in law are mainly divided into jurisprudence, legal history, constitutional law and administrative law, criminal law, civil and commercial law, procedural law, economic law, environmental and resource protection law, international law and other majors, and mainly train specialized talents for law teaching, scientific research and judicial practice departments.