A contact structure and manufacturing method thereof is provided. A substrate having a first conductive layer and a dielectric layer thereon is provided. The dielectric layer has a contact opening that exposes a portion of the first conductive layer. A conductive nano-particle layer is formed on the exposed surface of the first conductive layer. Thereafter, a second conductive layer is formed inside the contact opening to cover the conductive nano-particle layer and form a contact structure. The conductive nano-particle layer at the bottom of the contact prevents the second conductive layer from peeling off and costs much less to produce.