The invention relates to a femtojoule level laser micro energy meter, especially to a femtojoule level laser micro energy meter capable of measuring and observing simultaneously. The invention belongs to the technical field of laser measurement. The femtojoule level laser micro energy meter comprises an optical system, a photoelectric conversion system, a signal processing and displaying system, and a power supply. The optical system includes a first convex lens, a second convex lens, a concave lens, a beam splitter mirror, an ocular lens and a reticule. The three lenses in the group lie alongside and coaxially. The central point of the beam splitter mirror is in an optical axis of the three lenses arranged side by side; the ocular lens is in a focal point of the beam splitter mirror on one side and the reticule is disposed on the ocular lens. The photoelectric conversion system includes an optical filter, a photoelectric detector and a preprocessor. The photoelectric detector lies coaxially with the group of the three lenses and the beam splitter mirror and is movable. The photosensitive surface center of the photoelectric detector is at a focal point of the group of the three lenses. The minimum laser energy density that the energy meter in the invention can measure is 1.96 fJ/cm2; the range of observation and aiming is 1 meter to the infinite. Moreover, moving objects can be observed and aimed by the energy meter in the invention.