We would need at a minimum a save, logs, reproduction steps, and a description of what you were doing and how/when it got slow.

I am just on the ground, and principia's calculation doesn't even start, but if I remove principia, the game back to 60fps. The save is a brand new file with no astroids and spacecrafts

Look, we have many users on Mac and nobody has ever reported this. I don't doubt that you are seeing a problem, but if you don't give us a save and logs (both the KSP.log file and our own INFO logs found in glog/Principia) there is not much that we can do to investigate.

Because Principia still not supports v1.4.3, so I download the previous 1.4.2 version, and this bug was gone