I have a web app need video stream from camera in ios webview。 But，getUserMedia Api is not work in ios webview。 so，What other solution is there？
If getUserMedia is not an option due to WebKit not yet supporting it, I'm afraid your app will unfortunately stop being a web app. You can write native code that interoperates with JS runtime, which would allow you to receive a complete video recording from the users camera or you could even somehow establish the direct streaming. Thankfully, your question is just broad enough for me not to need to go into details.
You should also probably tell your management that the task is too difficult and expensive for the web app and they should probably not even try.