Is there a bus or train from Taichung to Songshan Airport? about how long?

Take the bus/Taiwan Railway/High Speed ​​Rail to Taipei Main Station and then take the MRT to the airport. It takes about three hours.

You can go to Tonglian Passenger Transport and Guoguang Passenger Transport to inquire, there should be a direct bus, or you can take the train to Songshan Station, which takes about three hours.