What is natural remedy for a low hemoglobin count in four year old child.?

Depends. It depends on the reason for the low hemoglobin.Your docotor needs to do a thorough assessment including family, social, enviromental dietary and genetic history, physical exam and possibly other labs in order to determine the likely cause of your childs anemia.
Depends on the cause. The treatment will depend on the cause of the low hemoglobin. Bring your child to your pediatrician and get further discussion/evaluation - that will include work-up to find the cause of the anemia. Then you'll go from there. Anemia can be caused by many different things- that will include congenital problems or environmental causes/nutrition deficiency etc.
Depends. For most at that age it is due to low iron intake/stores and a diet rich in iron may help some. However, some can have it based on an inherited genetic defect in the hemoglobin building process, some will have chronic intestinal blood loss, some are experiencing the after effects of an illness. Only having the results of history/exam and the tests can point the way to proper treatment.