Graphene-like porous carbon nanosheets (GPCNs) have recently been viewed as the outstanding electrode materials for high-rate-performance supercapacitors because the 2D nanosheets can integrate high conductivity and high aspect ratio together to promote both ion transport and electron transfer. The fabrication of GPCNs from sheet-like plant raw materials is of great importance to lowering production cost and simultaneously to promoting environment protection. Herein, we demonstrate the utilization of salt sealing strategy to fabricate GPCNs with flower petals as the precursor. The petals of salvia splendens are firstly crushed and sealed in NaCl crystal. After pyrolysis at the optimal temperature, salvia splendens-derived, O/N-codoped GPCNs are obtained by washing off NaCl with water. The resulting GPCNs possess a relatively high specific surface area and a moderate O, N contents. Owing to these characteristics, the GPCNs-based supercapacitor exhibits high rate capability (88.6% and 83.4% capacity retention from 1 to 100 A g(-1) in 6 M KOH and 1 M Na2SO4 solutions, respectively) and excellent stability. Taking into account the species diversity, renewability, and abundance of plant raw materials, they can serve as a novel kind of precursors for the fabrication of heteroatom-doped GPCNs for high-rate-performance supercapacitors.