A bolometer and a preparation method thereof. The bolometer includes: an infrared detection element (1) and a readout circuit (2), wherein the infrared detection element (1) is formed on one side of a first substrate (100), and an edge of the infrared detection element (1) is provided with an electrode hole (9), and the readout circuit (2) is formed on one side of a second substrate (200) and the readout circuit (2) has an electrode, the first substrate (100) is formed thereon with a silicon via (8) passing through the first substrate (100) and filed with a conductive material, the electrode hole (9) of the infrared detection element (1) is electrically connected to the electrode of the readout circuit (2) via the conductive material filled in the silicon via (8). The following defects are overcome: bolometers in the prior art need to flatten the silicon wafer surface with a suitable chemical-mechanical polishing process after a readout circuit thereof has been manufactured, the circuit is large in area, and the requirements of the system integration process are high.