If you don't have sufficient reasons, if your ex husband doesn't agree, you can't change the child's name. Pay attention to both the surname and the first name. On May 21, the Ministry of Public Security issued the Official Reply on Issues Related to the Change of Children's Names after Parents Divorce (Gongzhi 2002 No. 74): "According to the Reply of the Supreme People's Court on the Change of Children's Surnames The public security organ may refuse to accept a request for changing the name of a child by one of the two parties to a divorce without consultation or without reaching an agreement through consultation. If one party obtains a change of the name of a child by concealing the facts of the divorce from the public security organ, the public security organ may restore the original name of the child if the other party requests to restore the original name of the child and the divorce parties fail to negotiate. "
 So if you want to change your child's name, you still have to try to persuade your ex husband. Another way is to take your account book to the public security bureau when your child is 18 years old, but it's not meaningful at that time