Which is better to go to Shanghai Pudong Airport by plane or by high-speed rail?

Both plans are possible. If you are afraid of being late, planes and high-speed trains can be used. The key is that you should strive to arrive at the airport for security check one hour before the plane takes off and stop security check 30 minutes before the flight takes off. If you can get to Pudong earlier than the high-speed train by plane, you'd better fly. After all, you have more free time, even if it is late.