The invention discloses a self-focusing objective lens and a miniature fluorescent microscopic imaging device. The self-focusing objective lens comprises a self-focusing lens and a glass rod with polished end surfaces. One end surface of the glass rod with the polished end surfaces is connected with an image-side end surface of the self-focusing lens. The miniature fluorescent microscopic imaging device comprises an excitation light source, a focusing lens, a dichroic mirror, the self-focusing objective lens, an imaging lens and an area array photoelectric detector. The excitation light source transmits laser, wherein the laser is focused by the focusing lens and is transmitted to the dichroic mirror. The dichroic mirror reflects the focused laser and transmits to a sample through a lengthened objective lens. Fluorescent light which is transmitted from the sample is collected by the lengthened objective lens and is transmitted by the dichroic mirror. Then the fluorescent light is focused through the imaging lens and is transmitted to the area array photoelectric detector for imaging. The self-focusing objective lens and the miniature fluorescent microscopic imaging device have advantages of small size, small self weight and high suitability for in-vivo imaging.