The invention relates to a peak detection unit, a detection system and a detection method which are used for detecting whether an ESD diode in a to-be-detected chip is damaged. The peak detection unitcomprises a first operational amplifier A1, the positive input end of the first operational amplifier A1 is electrically connected with an input port P1, the negative input end of the first operational amplifier A1 is electrically connected with a VSS port P5, and the output end of the first operational amplifier A1 is electrically connected with a pin connection port P3; the positive input end of a second operational amplifier A2 is grounded through a charging and discharging capacitor C, and the positive input end of the second operational amplifier A2 is further electrically connected withthe VDD port P4; and the negative input end of the second operational amplifier A2 and the output end of the second operational amplifier A2 are electrically connected with an output port P2, one endof a resistor R is electrically connected with the VSS port P5, and the other end of the resistor R is electrically connected with the output port P2. Whether the two diodes connected with a test pinare normal can be quickly judged, and detection time is effectively shortened.