SL

[Snow Lau]

Can you explain to me which is correct?

1) I never forget to have this party.
or
2) I will never forget to have this party.

[Mister Micawber]

Neither, Snow Lau. What you want to say, I think, is:

'I will never forget having this party' (if it is still in progress) or 'I will never forget having had this/that party' (if it has finished).

[Tdol]

I will never forget having this party.

Remember to do = remember first, do second
Remember doing = do first, then remember

Forget is the same