Focused on the problem of narrow output pulse width of high speed quaternion detector and the follow-up circuit can not respond to it, the peak-hold circuit of high speed quaternion detector was presented. The circuit includes automatic gain control trans-impedance amplifier, peak detection circuit, sample-and-hold circuit. According to the requirements of high-speed pulse holding, the principles of sub-circuits were analyzed and detailed circuit diagram was designed. The experimental results show that the circuit can adapt to detector changing in large-scale and different background noise, output voltage waveform was stable for the follow-up circuits. The circuit is reasonably designed, simple structured, which has great practical significance.