The aim was to investigate the relationship between macrofauna biodiversity with quality or decay grade of beech logs deadwood and some environmental factors in the East Hyrcanian forests. 108 fallen beech dead woods have been selected for this purpose that have appropriate frequency in four decay classes, three diameter classes from 10 to 100 cm and three classes of altitude above sea level from 250 to 900 m. The macro fauna samples were collected in the field under dead wood skin and inside wood with a knife and hand sorting. The total macro fauna observed belonging to 7 classes, 10 orders and 27 families. The results showed that two orders Coleoptera and Geophilomorpha, two families Lumbricidae and Arionidae and two genus Julus and Octotemnus had the highest and lowest macro fauna frequency respectively. Richness and diversity of macro fauna have decreased with increasing altitude above sea level. Dominance indices were decreased with increasing the dead wood quality (decay stage class) while richness and diversity were increased. Slope and elevation, were introduced as the most important environmental factors that controlled macro fauna biodiversity of fallen beech dead wood.