Cellulose paper can be exploited for future electronics due to its flexibility, versatility, and low cost. However, the rapid fabrication of paper electrodes with a smooth surface and durability remains a challenge. In this paper, we report the fabrication of conducive, smooth and stable Ag electrodes on common printing paper through solution-processed silver mirror reaction. The rough cellulose substrate was modified with polypropylene to form an interconnected two-network structure yielding a super-flat surface and significantly better mechanical performance than paper or plastic. Based on the modified paper, a controllable spin-coating silver mirror reaction process was developed to form a smooth silver coating. The obtained Ag-paper electrode has a surface roughness without big particles over 50 nm and a strong barrier ability against moisture and solvents, while retaining the features of common cellulose paper. The successful solution-processed application of organic solar cells and organic light-emitting diodes based on silver electrode is demonstrated, showing the material's potential in future flexible electronics.