The utility model discloses an instrument measurement and control circuit special for an in-situ nutritive salt analyzer. The instrument measurement and control circuit comprises a power supply unit,a main control chip circuit, an analog-to-digital conversion circuit, a PLC access module, a temperature measurement circuit, a light intensity measurement circuit, a photoelectric sensor measurementcircuit, a liquid leakage measurement circuit and a stepping motor drive control circuit. The main control chip circuit is connected with the temperature measurement circuit and the light intensity measurement circuit through the analog-to-digital conversion circuit; the PLC access module comprises input interfaces used for being connected with all data input ends of an external PLC and output interfaces used for being connected with all data output ends of the external PLC. The PLC access module is connected with the photoelectric sensor measurement module and the liquid leakage measurement circuit through input interfaces, and is connected with a heater control circuit and a stepping motor driving control circuit through output interfaces; the power supply unit supplies power to all thecomponents. According to the utility model, the requirements of measurement and control of all parts in the in-situ nutritive salt analyzer can be met.