The invention discloses a water quality analyzer based on phase-lock amplification technology, belongs to the field of water quality analysis, and solves the problems that the conventional water quality analyzer based on the Lambert-Beer law is large in size, high in power consumption and low in precision. The water quality analyzer provided by the invention comprises a frequency modulation circuit array, an LED array, a light beam adjusting module, a water sample chamber, a temperature measuring module, a photovoltaic conversion module, a phase-lock demodulation array, a data processing module and a display module, wherein the frequency modulation circuit array is used for driving the LED array; LEDs are light sources; the light beam adjusting module is used for merging light waves emitted by the LED array into a beam of light waves and enabling the beam of light waves to be perpendicularly emitted into the water sample chamber; the photovoltaic conversion module is used for converting the beam of light waves emitted into the water sample chamber into an electric signal; the phase-lock demodulation array is used for separating the electric signal into a plurality of electric signals with different frequencies; the data processing module is used for conducting analog-digital conversion on the electric signals with different frequencies to obtain the concentration of the material to be tested in the water sample through a preset algorithm; the display module is used for displaying the concentration of the material to be tested. The water quality analyzer is used for water analysis.