If i do iui or ivf for first child after that can i concive second child normally?

Possibly: It depends on why you needed IUI or ivf to begin with. There are many couples who had to use assisted reproduction for one baby and then conceived naturally for the next. Especially if you aren't ready for another baby, don't assume you can't get pregnant without help and be sure to use contraception.

Depends why IUI, IVF: Agree with dr reaves' answer, unless both your tubes are 100% blocked in which case ivf is needed again. Almost all other causes of infertility have a chance of natural conception, even some men with 'zero sperm' (azoospermia) may get some sperm in their ejaculate. If you are diagnosed with diminished ovarian reserve (low egg supply) it makes sense to try to have your kids close together though.