This paper proposes an efficient buildin DC gain accuracy calibration system for digital oscilloscope, in order to substitute it for the conventional PC calibration system, which is complex and inefficient. Using Digital Oscilloscope instead of PC to control the oscilloscope calibrator directly, the system reduces the latency and speeds up its command stream and data stream. Benefiting from the tiny step programmable differential amplifier, the system improves the calibration accuracy. By calculating the calibration parameter according to sampling data directly, the system avoids the timeconsuming display processing. A highprecision internal calibrator is designed and the interfaces of it and various external calibrators are unified. The actual application results show that the system can meet the measurement need, at the same time, reduces the complexity and shorten the calibration time.