Yulei , in such a scene with a reflection covering the whole ceiling some artifacts like you see, can occur - In the first instance you can also read up on this article here as it goes a bit more into detail as to what these are usually caused by. You could happily send me the scene at hand and I can have a closer look myself and propose some improvements, otherwise, you may also want to play with the perspective of your scene.
Thank you，Demian. I know that enscape is committed to fast rendering, and reflection consumes a lot of computing resources. But I also hope that enscape can have the option of high-quality output. For some specific scenes, the reflection of the mirror is required to complete the design.