An ion-implant technique for fabricating Si:As blocked impurity band detectors for VLWIR detection had been investigated, and the detectors with good photoelectric response performance had been demonstrated by optimizing both the processing condition and the device structural parameters together with material characteristic parameters. At 5 K temperature, with a dc bias voltage of -3.8 V, the peak response wavelength of the fabricated devices is 23.8 μm, the blackbody responsivity is 3.7 A/W, and the detectivity is 5.3×10¹³ cm?Hz^1/2/W at 3.2 V, which are comparable to （and even superior to） those reported in literatures. Especially, the device manufacturing process is compatible with that for fabrication of integrated circuit, and the detectors can be integrated with readout circuits on one chip, resulting in a remarkable reduction in produce cost and a significant improvement in the imaging performance.