I am importing .obj file into houdini. It has so many groups, how can I delete all the groups. I tried with delete option in group node. It took much time to delete every group. Is there is any other option to delete it

Try wildcards.

E.g. * (all groups), Object* (every group starting with “Object”) or ^myGroup (all except “myGroup”)

And there's much more you can specify. Have a look here (lower section): http://www.sidefx.com/docs/houdini/model/groups [sidefx.com]

Thanks Bollili, its working