I noticed that someone was directed to this site when they searched “use booster seat in beijing taxi.” So, I thought I’d answer this question:
Forget about it. Most cabs don’t even have seatbelts. Before we went we bought these “portable” boosters that we lugged around for the first few months. In the early days we would stop cabs and then send them off again if their seat belts were missing, sometimes taking eons to find a cab that we could use. By the end we became realistic – you either buy a car service and make sure that you tell them you need seatbelts or you get into the cab and hold onto to your children tight. I had nightmares about getting into car accidents so mostly we used mass transit but we also took plenty of cabs.