Doctor is the highest level of postgraduate education. For undergraduates, there are two ways to read PhD. One way is to graduate for five years and get some achievements in applying for a major, but not many people choose this way. The other needs to get a master's degree before studying for a doctorate. For undergraduates, if they study for a master's degree and then a doctor's degree, they usually study for two years, three years and then a doctor's degree. For doctors, different colleges and majors have different training programs. Generally, it takes 3-4 years to study for a doctorate, so it takes at least five or six years to study for a doctorate. But now, in order to encourage outstanding students to do scientific research, many schools have formulated policies to continue studying for master's and doctoral degrees. It usually takes five years to continue studying for a master's degree and a doctor's degree, which saves one year compared with studying for a doctor's degree after graduate school. And some doctors with special majors need to study for a longer time, such as a doctor of medicine, which needs to study for at least eight years. Medical students generally have five-year, seven-year and eight-year programs, and then they are awarded bachelor of medicine, master of medicine and doctor of medicine respectively. Medical students who graduate from five-year programs can continue to study for master's and doctor's degrees in medicine for three years. After graduating from a seven-year master's degree in medicine, you can continue to study for a doctor of medicine. After passing the examination and interview, you can study for another three years and get a doctor's degree. 8-year medical students are undergraduates who continue to study for 8 years. The above is just the usual situation, not everyone's doctoral study period is the same. Many times, doctoral students may be delayed due to the constraints of doctoral thesis and research projects. Students who want to study PhD must know the relevant information in advance.