hi,

i download last community edition, and block plugin list is empty in ui management

is it normal ?

note: i've only one hello world plugin activated

Hi,

The list will be empty if there aren't any block based plugins available.

Are you sure the 'hello world' plugin is enabled.

Try creating a sample plugin following this:
http://codoforum.com/documentation/write-a-hello-world-block-plugin

Then, enable the plugin and see if you can find that plugin from the UI Elements -> Blocks interface.