in VR mode,how to let PC show 1920*1080 single screen

Alright, I wouldn’t use set view target with blend, it’s meant to be used with static cameras. I put together a sample project with a basic implementation, you can download it here: VRSpectator_SampleProject.zip - Google Drive
Without looking at your whole project, it’s hard to tell what’s wrong, but I hope this can give you a baseline.