Yichen Lu if you are not persisting the state then yes on a page refresh the state will return to the initial state whether that be {} or if you have specified an actual initialState. If you are wanting to persist your state I would recommend the following package:
https://github.com/rt2zz/redux-persist
If you are losing your state on a page redirect or traveling to a different route using react-router you will want to use:
https://github.com/reactjs/react-router-redux
Hope I answered your question or at least provided you with some good resources!