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The NiAl-layered double hydroxides (NiAl LDHs) has been known as a very desirable positive electrode material for alkaline supercapacitors due to it can provide a higher theoretical specific capacity than β-Ni(OH)2. However, NiAl LDHs is structurally unstable in an alkaline solution and can easily convert into another crystal (β-Ni(OH)2). Therefore, it is important to study and design the true active phase of the effective electrode material. In this work, we use high-valence Al ions to replace some of the Ni ions in the raw materials to stabilize its crystal structure and prepare the tremella-like NiAl LDHs decorated on polydopamine/reduced graphene oxide (NiAl LDHs@PDA/rGO) by a simple hydrothermal method. The NiAl LDHs@PDA/rGO exhibit high specific capacitance of 2210.7 F g−1 at 1 A g−1 and excellence rate performance (71% of capacitance retention with the increase of current density from 1 to 40 A g−1) as the cathode material for supercapacitor. Furthermore, the hybrid supercapacitor delivers a superior energy density of 58.93 W h Kg−1 at 800.21 W kg−1 and long cycling life. This work not only provides a simple method to prepare the tremella-like NiAl LDHs@PDA/rGO but also paves the way for the development of advanced cathode materials for the next generation of supercapacitors.