签证申请一经批准，不可更改，也不能延期，费用不予退还。　
如你的赴华目的发生变化，你可以向使领馆递交新的签证申请，再次履行申请手续并交费，已有的有效签证将被作废。如果你已经进入中国，应在停留期满前向当地公安机关出入境管理部门申请改变签证种类或申请延长停留期限，公安机关将依据中国法律和规定，做出是否准予办理改签或延期的决定。　

Once the visa application is approved, it cannot be changed or extended and the fee is non-refundable.
If your purpose of going to China changes, you can submit a new visa application to the Embassy or Consulate, fulfill the application procedures and pay the fee again, and the existing valid visa will be invalidated. If you have already entered China, you should apply to the Exit-Entry Administration Department of the local public security authorities for changing the visa type or applying for extension of stay before the expiration of the period of stay, and the public security authorities will make a decision on whether to grant the change or extension of stay according to the laws and regulations of China.