The invention relates to a biological detection sensor, which is characterized in that the biological detection sensor comprises a mounting rack, a cantilever mechanism, a test plate bin, a peristaltic pump and a singlechip, wherein the mounting rack consists of a side plate, a back side plate, a transverse support plate and a support beam; the support beam is horizontally provided with a guide rail; the cantilever mechanism comprises a linear stepping motor of which the output end is connected with a pin head, and a photovoltaic conversion device; the cantilever mechanism is arranged on the guide rail in a sliding way and is connected with a transmission belt, and the transmission belt is connected with the output end of a stepping motor; the test plate bin is a rectangular frame with enclosed four sides and arranged on the transverse support plate below the cantilever mechanism; the transverse support plate on one side of the test plate bin is provided with a liquid level detection window in which a liquid level detection switch is arranged; the peristaltic pump is connected with a pipe, of which the outlet end is connected with the pin head; and the singlechip is connected with the stepping motors and the input end of an electromagnet. The biological detection sensor realizes the automation of the biological detection and can be widely applied to the on-line detection in fields such as environmental protection, medical diagnosis, production of foods and medicaments and the like.