Hello I have a website in html,now i am going to change my website coding to DIV, will it effect in ranking position on google,Will it decrease in the start because google will findout my website whole new but i am not going to change my title, drescription, keywords.
DIVs are better then HTML. Your rankings may suffer if any content is altered, but for the most part, you should be fine.
It depends how significant the change is going to be - you shouldn't see a huge impact if the important tags like title are kept the same and the content doesn't change. However if your div based site is bigger than the previous version, site speed can kick in.
DIV based page is still HTML. You probably wanted to say you will change site from tables design to DIV's. And back to question, DIV based page is usualy with less code then tables, so it can bring some value since percent of content comparing to whole code will be better. Just my oppinion, I had one expirience of that kind that helped SEO a bit.