for example, you believe you have a electron described by a plan wave, which is "该波函数描述的系统". But I doubt about that. How can you prove that you are right?

For sure, without measurement, we can only argue with each other for ever. So you decided to do a measurement. Your measurement resulted a momentum value of 8. Now what? Can you actually prove the existence of "该波函数描述的系统"? Unfortunately, no. because many system can give you this value. Further more by doing this measurement, you have just destroyed the system being discussed. There is no way to prove you were right or wrong any more.