In the contribution the diagnostics of a microdischarge generated by a plasma pencil at atmospheric pressure is investigated by means of optical emission spectroscopy. The plasma pencil is a special type of a barrier plasma nozzle at atmospheric pressure. The nozzle is made from dielectric material and through this nozzle flows working gas (typically argon), while outer power electrode is connected through the matching unit to the rf generator driven at frequency 13.56 MHz. Optical emission spectroscopy in the range 200 ÷ 750 nm was used for plasma diagnostics. Characteristic plasma pencil design is as follows: inner diameter of outlet of the nozzle 0.4 mm, typical length of the nozzle 4 cm, characteristics rf generator output power varied 70 ÷ 300 W.