Due to study the effects of gap size and position on herbal diversity indices and soil features, twelve canopy gaps with an area between < 200 m2 and 1000 m2 were selected in a reserve oriental beech (Fagus orientalis Lipsky) stand in the north of Iran. For each canopy gap, one non-gap plot (closed canopy) 4 m2 square sampling quadrate was considered also. Ground vegetation was assessed within five sample plots (2 × 2 m area) from gap center to the edges. Soil samples were taken (0 – 20 cm depth) from within gap and closed canopy positions. Some of soil characters including pH, organic matter and carbon, total nitrogen, phosphorus, potassium, calcium, magnesium and saturated moisture were measured at the laboratory. Results indicated that diversity and richness indices increased with increasing of gap area whereas, evenness indices were decreased. Furthermore, the highest amount of diversity and richness indices were observed in gap center compared with gap edge and closed canopy. But, closed canopy position had the greatest value of evenness indices. Analysis of data showed that soil pH, organic matter and carbon and also total nitrogen increased with increasing of gap area. Also the highest values of these characters were detected in within gaps. Whereas, saturated moisture amounts decreased with increasing of gap area and the highest value of this character was detected in closed canopy. Compare means of available phosphorus, potassium, calcium and magnesium in the gap size indicated that medium gaps had the greater amounts than in the small and large gaps. These characters were significantly greater in within gaps in comparison to closed canopy. Greater amounts of carbon to nitrogen ratio were found in medium gap and closed canopy position. In general, our research results provide a useful basis for evaluating the implications of forest management practices.