Can not add more than one category

try this,use:
<field name="catid" type="text" default="" label="Category" description="A content category" />

then you will get simple text filed in module settings. Find category ID's from category manager (last column in list), then enter value in this format:

<category 1 ID>,<category 2 ID>

example:

12,21

It has succeeded ..
thanks