 Planar on-chip micro-supercapacitor (POMS), as a new energy storage device, can be easily used for integration with micro/nano electronic devices to provide an effective power source. In this work, a modified liquid–air interface self-assembly method is introduced to fabricate reduced graphene oxide (RGO) films on the silicon wafer for POMSs. The RGO films have good surface morphologies, uniform thickness (31 ± 3.073 nm) and high conductivity (640.3 S cm−1) after hydroiodic acid treatment. The POMS exhibits a maximum stack capacitance of 351.59 mF cm−3 and 98.17% capacitance of POMSs was retained after charging and discharging for 2000 cycles at a scan rate of 1000 V s−1. Specially, there is still a high power density (587.85 mW cm−3) at an ultra-high scan rate of 5000 V s−1 as well as an ultra-fast charging–discharging time (14 ms). The demonstrated POMS has a good application foreground in the preparation of high-performance integrated micro-devices.