without deleting the songs it already have from my new laptop.
From the NEW laptop? Yes. If it is already synced to the new laptop, just add additional songs.
If that was a typo, and you are asking about keeping songs it has from the OLD laptop, while adding more songs from the new laptop, you cannot do that with a 1st or 2nd gen shuffle. It can only be synced to one iTunes library at a time.
But you can transfer songs currently on the shuffle to the new laptop first. iTunes can't do that, expect for songs you purchased from the iTunes Store. However, there are third-party methods and utilities that can do it. If you do a Google search on "ipod transfer," you should get some links.
Once the songs from the shuffle are transferred to the new laptop, add them its iTunes library, THEN sync the shuffle.