Discussions

I have an old old cat and recently I got a new cat. My old cat hisses when a close approach which makes the other cat on guard. One I saw the new cat attack my old cat and today coming home I saw bunch of fur from my old cat on the ground so a fight happened.  
How can I make the old cat relax and how do I make the new cat stop attack my old cat??  
I see fear in my old cat and she doesn't move around anymore, in human life my old cat is over 90 years old, at that age you are not so good in fights.  
Now I worry every time when I live the house. If it keeps like this I may get rid of the new cat because I am not getting a new cat to kill my old cat. I am attached to my old cat for years.  
Any effective recommendations for them to get along.

Please have a look at Dr Liana Mawer's website, where there are free articles about cat behaviour, including introducing a new cat and keeping peace in multi-cat households.  
 
http://www.drlianamawer.ca/index.php?id=catbehaviour  
 
Another suggestion is to also use Feliway, which is a cat phermone that helps calm cats in stressful situations (available from vet clinics).

This is quite common, happened to us too. The resident cat did not like our "new addition", had to put them in separate rooms and slowly introduce them to eachother. Be prepared for a long wait. Honestly, it took a few months for them to accept eachothers existence. It will be 1 year in june for us, and now they are the best of friends and each others shadow! Be patient and they will sort it out on there own.

first keep them in two separate rooms - then switch out there bedding so they can smell one another. then start letting them see one another. feed both at the same time but far far apart while you are on guard. Slowly get the dishes closer together as their tolerance increases. It is all about hierarchy, the young cat wants to depose the old cat and you have to convince them they have to live together. Never leave your old cat where the young one can get him until this is resolved.

at first the new one had not much interest but it is the old cat if she could stop hissing and making vocal sounds now the new cat stare at her with eyes and wants to attack otherwise when the old cat walks by but I do find the new cat aggressive.  
The old cat knows she is weaker so she has fear I'm fear, she just wants be in peace and be quiet in her corner, she walks like an old limpy lady, she doesn't hear well, she doesn't want to play but I love my old cat.