Sorry about that English is not my first language，so please look at the pictures, I hope you can understand what i want to express

https://thumbnail1.baidupcs.com/thu...ge&autopolicy=1

https://thumbnail1.baidupcs.com/thu...ge&autopolicy=1

As the pictures showing, when I raise the camera，the lower terrain looks broken，and the same problem appears in EIG, because of this problem, I
cant go on my working, please help me , thanks a lot!

Maybe you can explain a bit more what you mean by "broken"? From your pictures I would say everything looks as it should. It is normal that the grid vanishes if you raise the camera.

I have replaced the pictures, please, I need help!!

The pictures are not displaying for me. I am getting an error message. Perhaps it’s my device?

the pictures are missing , I tried to upload again but can't save changes , now I set them on this floor

It's just because the terrain level is so close to the sea level that when zooming out, using lower level of detail, the terrain doesn't display correctly.
To fix it you'd need to either raise the terrain height a little, or lower the sea level. It's purely graphical though.

Thank your for your help， so it's not a bug just for me? Maybe I have to avoid this in my next world , bug now I need to find some way to finish my present world.

No, it happens to me a lot when I use shallow beaches. It's to do with the way the game reduces the level of detail as you zoom out to suit your system specs; it may look different on other hardware.