The invention provides a front-end conditioning circuit for measuring a high impedance weak signal and belongs to the technical field of spatial measurement. The circuit comprises a signal source, a first-stage amplifying circuit, a protection circuit and a second-stage amplifying and rectifying circuit, an equivalent circuit of the signal source comprises signal source voltage VS and internal resistance RS, the first-stage amplifying circuit comprises an operational amplifier A1, a capacitor C1, a resistor R1, a resistor R4 and a resistor R5, the protection circuit comprises an operational amplifier A4, a resistor R2, a resistor R3 and a capacitor C2, and the second-stage amplifying and rectifying circuit comprises an operational amplifier A2, an operational amplifier A3, a resistor R6, a resistor R7, a diode D and a capacitor C3. The front-end conditioning circuit has the advantages of being low in noise, high in input impedance, low in output impedance and capable of reducing measurement errors and achieving measurement of the high impedance weak signal.