A peak detect-and-hold circuit and method thereof using ramp sampling technique includes utilizing two sampling signals of different slopes to sample an input voltage for respective tracking voltages; comparing the held tracking voltage sampled with the sampling signal of a smaller slope and the input voltage to determine whether the input voltage is rising or falling, and if the input voltage starts falling, the held tracking voltage sampled with the sampling signal of a larger slope is taken as the peak. The peak detect-and-hold circuit using ramp sampling technique controls respective tracking voltages by comparing the input voltage with the sampling signals rather than the feedback tracking voltage. Also, it uses the input voltage directly rather than an operational transconductance amplifier to charge holding capacitors for the tracking voltages. Therefore, the errors of peak detecting and holding, namely the pedestal voltage, overshoot voltage and voltage droop are reduced.