Global Navigation Satellite System can not only positioning but also emit microwaves of L band to the earth surface. With the reflection signals, we can obtain information about the sea surface. The Delay Doppler Map calculated from the received power recently play a key role in building relationships with the sea surface parameters. In this paper, the basics of Delay-Doppler Map are introduced and conducted by employing a set of new released TechDemoSat-1 GNSS-R data. In addition, sea surface parameters retrieved by using Delay-Doppler Maps are presented as a prospect.