CPU will be full (100%) when run Minecraft

My CPU usage sometimes will be 100% and RAM usage is about 1GB or more when I play Minecraft Win10 Edition. My world size is about 90Mb. Blocks loaded very slow, everything almost freeze. This situation will happen more frequently when I play with my friends in local area network, especially when someone enters the main world or the nether.
Under normal circumstances, my CPU usage is less than 20%.