i will be travelling from us going to philippines but my passport has a validity of 4 months.

Elsa, so are you afraid that you may not enjoy 72 hours free transit in China because of your passport is valid for four months only? Actually, there is no specific requirements on the validity of passport for those who plan to make use of 72 hours free transit. If you are still worried, you may contact the airport you arrive at to ask if there is such a requirement.