The present invention discloses a biological detection device and a detecting method. The biological detection device comprises a substrate, an electric field unit, a liquid crystal/polymer composite film (LCPCF), a power supply, a processing unit, and an image sensor. Because of the electrically tunable orientations of the liquid crystal (LC) director anchored among the polymer grains, the wettability of the LCPCF changes with an applied electric field. As a result, we can manipulate a blood droplet on the LCPCF by a wettability gradient owing to the distribution of LC directors on the LCPCF. The motion states of the blood droplet can be related to the various qualities of the blood, and finally determines the health of the test sample. The change of contact angle of blood on LCPCF and the blood droplet motion on LCPCF indicate the concentration of TG and the concentration of HDL.