since flash does not support  and  tags so,is it any suggestion for me

Yeah, it sucks that text fields don't support that. There are a lot of things I wish text fields supported. If you only need 2 specific super script characters, you can use ² and ³. You can look at the character map to see the character codes to get these special characters. In Win XP go to Start > Programs > Accessories > Systems Tools > Character Map. If you click on a specific character, it will give you a code to use. For example, to get ² you hold down Alt key, then press 0178, then let go of Alt key. Then ² will appear at the insertion point.

Unfortunately, those are the only two I see. So if you need something else, you are sol. Other than that, you would have to create a separate text field and position it which is not fun.

Yes, <sub> & <sup> tags are not supported by Flash but you can
use Subscript & Superscript in dynamic and input text field in Flash:

Download & install Subscript & Superscript fonts from http://www.subscriptfont.com
You will need to restart Flash software after installed fonts.
Create a dynamic text field with Arial font embeded. Set the HTML property to true.
Create a dynamic text field with Subscript font embeded.
Create a dynamic text field with Superscript font embeded.
Use HTML tag to set text to subscript or superscript like below:
Some text<font face="Superscript">©</font>
If you are using ActionScript to test the htmlText, use script like below:
my_txt.htmlText = "Some text<font face='Superscript'>TM</font>";

They are better than CG since it goes lower than the baseline and it's real subscript..