This paper proposed a simple and novel self-sintering process of silver nanoparticle (AgNP) ink with commercial photo paper. Generally, AgNPs in the commercially available ink is capsuled for its preservability, so it requires sintering process to removing the capsule for high conductivity. In this work, we used commercial photo papers containing chloride on its surface generally, which induces self-sintering of AgNP. When AgNP ink is printed on the photo paper, chlorine ions is emitted from photo paper, and they are acting as sintering agent for AgNPs. Due to this phenomenon, self-sintering process occurs without any additional treatment after printing. We demonstrated proportional relationship quantitatively between conductivity of printed pattern and chlorine atom ratio in several types of photo paper. The sheet resistances measured from printed pattern are low enough (lower than 0.25 ohm/square) for efficient printed electronics.