How can US father stop Chinese mother with US passport, from getting Chinese visa for minor child?

Becky, did your wlife get her US citizenship or green card when your kid was born? If not, then your kid needs to apply for the travel document instead. In order to apply for the travel document, both your passports and marriage certificates are required. If any of you can't present at the consulate, you are required to write an announcement and have it notarized. That is to say, without your consent, your wife can't take your kid out of USA.

If your wife acquired US citizenship or green card before she gave birth to your baby, then your child needs to apply for an entry permit. However, I heard that the other parent is required to provide a consent letter if the kid just travels with one parent. Without your consent, your kid can't apply successfully.

By the way, I also heard that you might report to the immigration department that your wife may take your child back to PRC without your consent. Then they might help you stop her doing this.

Anyway, I think you should resort to a professional lawyer on this issue. They can guide you to do the right thing.