it always make the chaos after sorting

Make a 3rd column in the table or in a query that has sort order and tell it what to do either individually or with a IIF statement

My standard is to separate out the quantity from the unit designation.
Because you have the unit in the same field that automatically means that the field is text. So you will always sort like:
1, 1.2, 1.5, 10, 11, 2, 2.1 instead of 1, 2, 3, 4

Thanks, Dear Scott

yes, i made the number and unit togther, i also think it is not a better way, i also has other unit name like "ml", also has like "20~30g", also ths "590ml, 20pieces/carton", i don't know what to do next for make it better and easy.

and i think Dear Adam idea is a good idea, but it seems a little harder

The best way to do it would be like Scott said to separate them, then you could use a nested IIF statement in a query to assign a number to each unit of measure that you wanted to sort. IIF([Unit]="KG",1,IIF( ... etc

thanks, Dear Adam. i will try it when i am out of office, it seems it can be worked after you told me. thanks

This would be very similar to Convert Currency except instead of money you're dealing with different units of measure.