I'm using mysql 5.5.9
I used create database query to create a new database but this new database is not coming in mysql.db table can anyone tell me the reason y and even how to get the database in that table.

check if the query you used to create database is similar to this:-

CREATE DATABASE database_name;

I hope your problem is solved....
If you are not getting the database created then tell if you are getting any error and if so specify the error....

I'm able to see my database from show databases query but it is not present in the db table of mysql database and because of it I'm unable to grant prinileges to other users