I have ceramic tile on most of my house ,but it is uneven and it looks ungly I was thinking of leveling it with cement and then put new tile on top of it .
But I don't know what tipe of cement to put .And if this will have a good result .

I would not try this unless evey inch of the old tile is in great shape, not loose tiles anywhere. Lay new tiles in a bed of 3/8" thinset.

I agree with ballenger. My brother is a tiler and he is reluctant to lay tiles on top of tiles. In fact he flat out refuses to do it. Why can't the old tiles come up? It may take some hard work but it should be possible.

If you decide to try this you do need to use thin set mortar,I've also seen this done, its not ideal but you can do it,
If possible id remove all the tile first, then lay the new tile. Also by adding a layer of tile on top does it cause a problem with your doorways, especially your front door swinging in?

I guess what we are all saying is that it is possible but not a good idea. The original tile will obviously remain the oldest and is more likely to break loose. If the tile underneath breaks loose so will the tiles above, it just doubles your chances of failure. If you do this do not use modified thinset, get the regual stuff that is not premixed.

I second the answers above... do not lay tile on top of tile no matter if thinset is on top of the old tiles.