Tier 1 - Ltd company

I'm working as a contractor through a limited company. I'm the only one taking dividends at the moment. If I add my spouse as a shareholder and provide didends to her, can my dividends still be used as income when I need to extend my Tier 1

Thanks

Yes.
You claim your personal earnings and any dividend paid to you (for % of your share of total dividend belongs to you), is your personal earning.
Make sure your and her dividends are paid into two separate (individual) bank account.