I suppose you cant maintain the same material  master for
two different company codes. I beleive you should have two
different master records for the same material across two
different co. codes.  Pls correct me if im wrong.

i think we can move the goods from one company code to 
another,with the help of cross company sales.

iam also not so correct about this,please correct this.

I agree with the above answer.. but for cross company sales
after making all the required customisation, you asign the
material to the sales organisation of a different co.code
other than that of the original plant's co.code. but u donot
maintain the material for two diferent co. codes as such..
pls correct me if im wrong..

.
there is no need to maintain one material for different co. 
code just defined plant for cross system goods flow becouse 
material is mainly related to plant and we create it at 
plant and sales area level

Pls correct me if i m wrong

we have to extend the material from one plant to another 
plant

In addition to Yogesh's reply, Yes. You can extend the 
material to the other plant.
In MM01, you have the option to copy the material info from 
one plant to the other ,Provide the plant name of the other 
company in the plant name field .thereby you maintain the 
material info for 2 diff company(plant).
Please correct if this is wrong

Yes, I agree with Sidh, You can extend material to the 
other plant in mm01, you can copy the plant and and storage 
location from where you want to copy apart from that you 
have to assign plant to sales org, distribution channel in 
enterprise structure. so that you will not face any problem 
while creating customer master record (XD01). You need to 
assign Plant to company code in enterprise structure.

It is not necessary to maintain a material fro 2 diff 
company codes.
What we can do is maintain the material for 2 plants, in 
the 2 company codes in which you wanted the material to be 
maintained.
Just go to MM01, enter the material, then in the selection 
fields select all, then enter the required plant, sales 
area, SLOC, that will be it.
Just remember to fill the Accounting Views (both 1 and 2) 
data in case they are not copied from the previous plant 
(if they are different).
Enter a few of the mandatory fields that the system will 
prompt, like Availability check and loading group etc.
And you will be through.
But, in this case if the materils is active for GTS (Global 
Trade services), you may expect a GTS block while working 
with the material in the new plant. Since if the material 
is extended to a new plant then it needs a new license for 
it.
Other than that I feel that this will work pretty well.