I have big star and a small star and I use the blend tool with specified steps set to 6. But they are not aligned with equal spacing. Is there any other step or method to make a blend from a small to a big star with equal spacing?
Not really. Illustrator's blend tool isn't as precise or easy to control as I'd like. You can work around it a bit though; as I explain in this answer, the distribution of objects is controlled by the bezier curve of the spine, so you can convert the end points to smooth points and adjust the handles on each end.
You can see here that I've pulled in the handles from each end point of the spine:
It's not perfect or precise at all, but it's the best you'll get with the blend tool.