A fisher for underground testing instruments belongs to equipment matched with oil field testing instruments, and is characterized in that a weighted lever connector is connected with a main body through fastening screws; a left window and a right window are formed on the main body; a left suspension block is arranged in the left window, and a right suspension block is arranged in the right window; the left suspension block is connected to the main body through a left pin shaft, and the right suspension block is connected to the main body through a right pin shaft; a spring is mounted between the upper part of the left suspension block and that of the right suspension block; a left suspension shoulder is arranged on the inner side of the lower part of the left suspension block, and a right suspension shoulder is arranged on the inner side of the lower part of the right suspension block; and an open slot is formed at the lower part of the main body. When the lower part of the main body comes to contact with a short steel wire on a testing instrument, the short steel wire is led into the open slot, so that the main body can keep moving down; and a fishing head of the testing instrument pushes the left and the right suspension blocks to expand outwards and is suspended, so that the testing instrument can be fished up. The utility model can fish up testing instruments which fall in wells and are nearer to the fracture parts of steel wires, thereby avoiding the situation that water is stopped from injecting to the wells, reducing the operating cost and brining good economic benefit.