The utility model discloses an online monitored control system master control circuit of mini multi -function concrete temperature of split formula intelligence, watchdog chip U6's power supply input pin links to each other with power supply VCC, and still through filter capacitance C61 ground connection, mains voltage monitoring input pin passes through current -limiting resistor R61 and connects power supply VCC, and mains voltage monitoring input pin is still through current -limiting resistor R62 ground connection, first load capacitance C12, second load capacitance C13 connect in parallel respectively in crystal oscillator Y1's both ends. The utility model discloses the external exclusion pull -up of singlechip IO mouth has increased interference killing feature and driving force, has strengthened singlechip stability. The 12Mhz crystal oscillator is used, very accurate communication baud rate can be obtained. External input filter electric capacity during the input of watchdog chip power connection plays filtering, decoupling effect, makes input voltage more stable, guarantees the the normal power supply of watchdog chip. Watchdog chip power supply voltage monitoring input pin series connection current -limiting resistor avoids the saltus step of VCC electric current and burns out the chip.