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Electromagnetic non-destructive evaluation (NDE)instrument based on high Tc superconducting quantum interference device (SQUID) incorporating a gradient field excitation has been developed.The SQUID is fabricated by YBCO thin film and mounted in vacuum at the end of a cold finger fixed at the inner wall bottom of the dewar,which is filled with liquid nitrogen (77K) to cool the SQUID sensor.The sensor faces a thin fiat sapphire window on the outer wall of the dewar and is thermally isolated from it by a vacuum space at a distance of less than 1mm.To contribute as little as possible to the sample-sensor distance,it is essential that on the one hand the window must be as thin as possible and on the other it also must be rdatively small in diameter,in order to limit the concave bending up under the atmosphere pressure.By using a window with a thickness of 80μm and a diameter of 7mm,a sample-sensor distance of less than 2rim can be obtained.The magnetic field sensitivity of instrument is about 40pT/√Hz in magnetically u(t)shielded environment.By using this instrument the remnant magnetic field in a stainless steel sample and a 2mm-diameter hole at a depth of 2mm inside one aluminum plate at room temperature can be easily d(c)ected and imaged in an unshielded environment.