How to add edge loop on cone ?

thank you, didn't know we can bevel the vertex 

Hi hellosudeepsingh , no, a Cone consists of triangles, you cannot make an edge loop through CTRL-R.

What you can do, is to go into front orthographic view (if the cone isn't rotated..) and use the Knife tool:

Press K (knifecut)  C (constrain the cut to an axis)  Z (cut 'through the mesh') and make a straight horizontal cut.

If you are using 2.80, you can also use the Bisect Tool:

If that's not completely horizontal, you can select the 'cut' and press S Z 0.

In both cases, you can use G G to slide the 'loop cut' up and down.

thank you sir

hellosudeepsingh , you're welcome, Jonathan Williamson's way is probably easier;)

To bevel a vertex, select the vertex and press SHIFT CTRL B.

You will however lose the point of the cone that way....