The silver nanobowls were prepared by self-template method, and the structure and growth mechanism of Ag nanobowls were investigated. Results show that the Ag₂O clusters result from the reaction of AgNO₃ and NaOH. After adding the reductant methanal, Ag nano-shell is obtained on the Ag₂O cluster surface with the by-product CO₂ inside the Ag nano-shell. With the reaction further proceeding, the increasing pressure breaks through the Ag nano-shell, thereby forming the Ag nanobowls with the size of approximately 200 nm. This unique synthesis method provides theoretical and experiment basis for the noble metal nanomaterials with special structure.