Abstract: A water temperature and conductivity detector includes a detector unit, a cup-shaped bottom shell, and a socket connector having a top end connected to the detector unit, a bottom end connected to the cup-shaped bottom shell, a water inlet connected to a water supply system, and a water outlet connected to a reverse-osmosis water purifier system, the detector unit having two electrodes projected into the cup-shaped bottom shell to detect the conductivity of water passing from the water supply system to the reverse-osmosis water purifier system, and a heat sensitive resistor to compensate the temperature of water passing through the detector.