How Many Years Does It Take To Become A Child Psychologist With A Doctorate Degree?

A lot will depend on you.  How many hrs you carry & pass, etc.  My son is starting a PhD program spring semester.  He is a full time student.  It took him 4 yrs to get his undergrad (he has some friends that it took 5-6 yrs.) , 2 yrs (4 semesters) to complete his required masters classes and an additional semester to complete his internship and thesis.  He opted to do both, some programs will let you intern or write a thesis.  You will have to check with the individual college at the university for grad requirements.  His PhD program will last approximately 3 yrs.  You are looking at approx. 9-9 1/2 yrs at an accredited University.  You can probably find some places that advertise shorter course study...but BEWARE, not all degrees are equal.  Attend an accredited recognized university.  Good luck on your studies, it will be worth the work!!!

Do i need to receive any special training to become a child psychologist

I would say, that you will need a phd-8 years to be a child psychologist with a doctorate degree