I created an altcoin and mine, I found that the wallet address always change after mined a few blocks. Is there any way to let it fix?
It's normal behaviour... It generates a new address for each block, and when you send coins it'll generate new addresses for your change to.
There's a configuration option to disable this... It should be easy to find using google, but if i have some time later on, i'll try to find it myself.
BTW: this should be moved to the altcoin section (bottom right corner of the page)