The invention provides a collecting and amplifying circuit for floating weak currents. The circuit comprises a first operational amplifier, a second operational amplifier, a third operational amplifier, a fourth operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a ninth resistor and a variable resistor. The first operational amplifier, the second operational amplifier, the first resistor, the second resistor, the third resistor and the fourth resistor form a collecting circuit for collecting the floating weak currents and converting the currents into voltage signals, and the third operational amplifier, the fourth operational amplifier, the fifth resistor, the sixth resistor, the seventh resistor, the ninth resistor and the variable resistor form an amplifying circuit which is used for amplifying the converted voltage signals in a linear mode. The collecting and amplifying circuit for the floating weak currents can accurately collect the signals of the floating weak currents to be measured, convert the currents into the voltage signals, and amplify the signals in the linear mode, and the sequent signals processing is facilitated.