My Network Interface card r/w rate is 1000MB/S, but when I scp one file it shows the copy speed is 120MB/S. such as:
scp test.gz localhost:/data/test.gz
Looks like you're confusing Mb/s (megabit per second) with MB/s (megabyte per second).
1000 Mb/s becomes a theoretical 125 MB/s, and 120 MB/s looks like good performance (since you don't give more information, I take that it is a standard desktop PC with SATA hard disks).
Besides, I don't really think you can reach 1 GB/s (which would mean 8 Gb/s) without special equipment (10 Gb ethernet, a high-end NAS or a SAN etc...).
Instead of scp, sometimes scp will fail if the file size is huge due to connection timeout issues. Then You can try rsync command with bandwidth limit. (Here bwlimit=2048 refers to 2GB/second transfer speed, you can change the limit as per your from source to destination limit)
rsync -varP --bwlimit=2048 /tmp/localfile username@172.X.X.X