Novel hierarchical flower-like nickel sulfide assembled by nanoplates has been successfully synthesized via a template-free and one-step solvothermal method. The number of composed nanoplates can be tuned by adjusting the additive amounts of reactants. As comparative electrochemical performances are performed on, the sample with more nanoplates shows a higher specific capacitance and promising cycling stability. After 3000 cycles, a high specific capacitance of 778.8 F g−1 still maintains when the current density is 4 A g−1. These satisfactory electrochemical behaviours can be attributed to the hierarchical flower-like architecture, which supply more reactive sites for charge/discharge processes.