Redmine

Unless you created the custom field with "For all projects" you have to activate the newly created custom field in all projects using it. The respective setting can be found on the first page of the individual projects settings.

To use the field as a filter you have to also check the "Used as a filter" checkbox on the custom field.

Apart from that, it works for me :)

You are referring to two different custom field options: used as a filter and searchable

• When you set a cfield to be used as a filter, you can select it from the add filter dropdown on the issues page
• When you set a cfield to searchable, Redmine's search feature will also search in your custom field values.

works pretty okay for me.

I've tried but it didn't work but i don't know if i have to input any information to the Custom field (Issues) page other than in the text field, Name and check the Used as a filter checkbox.

Unless you created the custom field with "For all projects" you have to activate the newly created custom field in all projects using it. 
The respective setting can be found on the first page of the individual projects settings.

To use the field as a filter you have to also check the "Used as a filter" checkbox on the custom field.

Apart from that, it works for me :)

Holger Just when you said it works for you , you mean that you're able to filter the issues?

Well, yes, I am able to filter issues.
Actually, I don't understand well what is going wrong on your side. Could you pleas check / answer the following questions and further describe what exactly you are trying to achieve?

1. What type of custom field are you trying to create?
2. Have you selected one or more trackers in the custom field?
3. Have you activate the custom field in the project?
4. Are you able to create a new issue and enter data for your new custom field there?
5. Do you see a filter named after your custom field in the drop-down box for issue filters in the project?

--Holger

thank you, Holger
it works for me. i found that i forgot to enter data in custom field when create new issue.

but using custom field as a filter is not the feature I prefer

So, if i generate a new table in database and use some column in this table as a new filter . How I should do?
I'm not sure that it's relate about sql ?

How I should do?

If you want to include data from custom database tables you have to develop a custom plugin to redmine.

Note that this might be rather difficult as the current implementation of filters is one of the darker corners of Redmine imho. It is not very flexible. If you can you should stick to custom fields. If you still want to develop custom filters, have a look into Redmine's Query model to understand how filters work.