Whether it is normal for a 6 year old child to grow another tooth behind his teeth depends on the situation, if it grows behind the last milk tooth, it belongs to the first permanent molar, which is normal, if it is the time of tooth replacement, the milk tooth did not fall out of the new growth of the tooth is not normal. It is normal for the first permanent molar to grow behind the last milk tooth at around 6 years of age. If the milk teeth did not fall out, in the back of the milk teeth grow a tooth, generally is the milk tooth stagnation, this situation is abnormal, need to go to the hospital in time to the stagnation of milk teeth extraction, to prevent the impact of the growth of permanent teeth. It is recommended that this situation should be brought to the hospital in a timely manner to clarify the diagnosis, for targeted treatment.