Hi everybody.
I am using ZESTET1 module, which implements 1G Ethernet.
I was able to properly use this module and could send data to PC up to 
110 MByte/s.
However, in my application I need to receive real-time data with 70 
MByte/s data rate.
At this speed and real-time application, when I run the software CPU 
usage of my PC dramatically goes high and any event in my PC such as 
clicking on my software causes loosing data.

I use socket programming for read/write data from LAN port in PC. I 
checked size of data which PC OS (windows) issues event for me and its 
maximum size is 8 Kbyte.
I found that this is my problem. Due to the small size of provided data 
by windows, my software has to check the socket and read data; 
consequently, PC CPU is dramatically concerned with my software and CPU 
usage goes high.

Do you have any idea what I can do for solving this problem?

Thank you in advance.

You need to write a device driver to read it real time.
Download the latest DDK from microsoft and see its sample source codes 
for network.