I had been perform HIIT sprint with 30 sec sprint 60 sec walk a month... Juz like to ask does HIIT need to hav variation too? Or can i reduce my walking time to 45 sec as variation?

Check this out:
http://www.intervaltraining.net/HiitTraining-60.html

yes you need to vary for improvements. you are doing this to increase your lactic tolerance for running?

erm actually im doing it to replace my cardio... burn fat... so how HIIT shud be vary?

Try doing HIIT workouts with weights/kettlebells or try doing your running/walking using the Tabata protocol.

no one seem to point out that this is in the wrong section as it's neither bodybuilding nor strength training?

bodybuilding doesnt only involve stacking up as much mass as possible, cardio like HIIT also comes into play. Although there are varying opinions on whether HIIT should be used for bodybuilders as part of the cardio routine, i would still think it belongs in this section.