High CPU usage occurs periodically on the subscriber

I have set up a merge publication and a subscriber with push subscription mode.

On the subscriber, I notice the CPU usage is going high periodically.

It may take about 40 seconds for the CPU Usage come back to 0%. And it occurs at same time as long as the Synchronization Status display : "Uploading data changes to the Publisher". This only occurs at subscriber, the publisher is normally.

I've go to Reports > Top Queries by Total CPU time at the subscriber to see which queries make the CPU usage go high and below is the result:

I don't know what to do next to fix this issue. Does anybody have an idea on how to solve it?