My diabetes (pp) is 270 so can i eat soyabeans flour instead of wheat flour?

Diabetes: You can, but beside that other things you should do( if you are not doing them already) is excercise, avoid sugary drinks, weight loss, and take your medication persistantly (if you are on meds).

Hard to say: First, how long after eating are you checking your sugar? You should be waiting at least 2 hours to get reproducible valid results. If you are 270 2hr pp, that of course, is too high, and just switching from a simple carb (white flour) to a more complex carb (soy) will probably not get it into the target range of <150. You may need to look at eating fewer carbs of any type, or adding medication.