This work consists of contributing to the study of the phytodiversity of trees in the monodominant forest of YASIKIA, 31 km OPALA road RD Congo, specifically we wanted to know the richness of trees in this forest, analyze its floristic composition and structure by studying the specific abundances of trees structuring this forest. We proceeded to set up a 5 km or 5000 m transect in a North-South direction of the forest where emerging woody plants are well represented, crossing all topographic levels. 20 square plots of 50 mx 50 m were delimited on either side along the transect. We measured and identified all trees with DBH ≥ 10 cm at a height of 1.30 m from the ground, above the buttresses of the stilt roots. We calculated the diversity indices: Simpson, Shannon-weaver and Fisher alpha. After our field investigations, we inventoried 1573 tree individuals divided into 99 species, 88 genera and 30 families. The most abundant species overall are: Gilbertiodendron dewevrei with 303 plants, Scorodophloeus zenkeri with 153 plants, Cola griseiflora with 86 plants, Pancovia hamsiana with 80 plants, Polyathia suaveolens with 57 plants, Julbernadia sereti with 56 feet, Staudtia kamerunensis and Strombosia pustulata each with 55 feet, Cynometra sessiliflora with 45 feet, Guarea cedrata with 31 feet, Cleistanthus mildbraedi, Diospyros bipendensis and Diospyros crassiflora each with 30 feet.