Abstract: In 1880, G. Stokes conjectured that the free boundary of 2D irrotational water wave has symmetric 120 degree at the stagnation point, which is so-called Stokes conjecture. Varvaruca and Weiss gave a rigorous proof on the Stokes conjecture via a geometric approach in 2010. In this talk, we will introduce the fundamental idea to deal the singularity of the free boundary of the water waves at the degenerate point. Moreover, we will mention our recent results on the singularity analysis on the free boundary of the axially symmetric water wave with general vorticity at the degenerate point.