I have heard this song ,"Ain't no party like a chipmunk party" ,there is a negation in the word Ain't itself, why we need to use no after that .Aren't those two negations cancelling out ?
Indeed, "ain't no" is a double negation and technically not good English.
What you are missing, however, is that the intention of the saying is to be bad grammar. When the double negation of "Ain't no party like a chipmunk party" is being made, there is an irony of an attempt to look uncouth, even though the speaker is aware of the grammatical mistake. It is more of a caricature than a real statement.
In reality, the speaker is voicing a vote for the "coolness" of the chipmunk party, but this is an affectionate connotation rather than a strict literal sense.