Abstract: The connected defective elements in Focal Plane Array (FPA) were tested by optical microscopy and FPA test-bench. The reasons of forming connected defective elements in FPA were studied. Results show that it is difficult to identify connected defective elements by optical microscopy. And it is also difficult to identify connected defective elements by FPA response testing bench because the response voltage of connected defective elements is basically the same as that of normal elements. The connected defective elements can be identified effectively by FPA crosstalk testing bench because the crosstalk between connected defective elements is 100%, which is obviously different from that of the normal elements. At this point, the response voltage of connected defective elements is average of that of the normal elements. The tables with connecting or the electrodes with connecting caused by the process of photolithography and eroding result in the generation of the connected defective elements. As well as the indium bump with connecting caused by the process of photolithography and lift-off also leads to the generation of the connected defective elements. Fabrication process such as photolithography, eroding and lift-off was optimized to reduce connected defective elements.