As the most sensitive sensor for magnetic field detection

superconductivity quantum interference device（SQUID） is widely used in many kinds of weak magnetic detection.The pickup coil directly influences spatial resolution and the magnetic field sensitivity of low-temperature scanning SQUID microscope.With discussion of superconducting loop flux quantization condition

design demand of low-temperature SQUID pickup coil is obtained.At the same time

design and fabricate first order gradient superconductivity pickup coil instead of original solenoid coil to decrease environmental noise and increase system sensitivity.This coil made by 66 μm diameter low-temperature superconducting niobium wire enwound on the sapphire bobbin with 40 times microscope.The coil radius is 316 μm

the baseline length is 1 436 μm

and the inductance value is 0.873 μH.Experimental result show that magnetic field sensitivity of system is risen from 250 pT/Hz to 2 pT/Hz by superconductivity gradient pickup coil.Finally

basalt slice specimen is measured by this gradient pickup coil and valid datas are obtained.