Abstract: In order to satisfy application demand for high performance and miniaturization of pulsed power system, two types of micro-stacked insulators were designed and fabricated. One was fabricated from interleaved layers of brass and PI (polyimide), the other was fabricated from stainless steel and FEP (fluorinated ethylene propylene). Based on the nanosecond (10 ns/30 ns) pulsed power vacuum experimental facility with Marx generator and single coaxial pulse-forming line, the vacuum surface flashover characteristics of the micro-stacked insulators were tested. To get a precise calibration of the measurement system, a magnetic pulse compression power supply with a relatively high pulse amplitude output of about 20 kV was used, and a voltage-dividing ratio of 25 133∶1 was acquired. Two types of m