Soil is a complex environment resulting from the interaction between plant cultivated and soil fauna. In this work, we investigated the relationship between the chemical components of plant roots and the biodiversity of soil fauna. The effect of root exudates of three different vegetable crops (cucumber, okra and eggplant) on the activity density of soil fauna was compared. The experiment was carried out at Fayoum Governorate, Egypt. Soil arthropod samples were weekly taken from the aforementioned crops using the pitfall trap method. Also, the chemical composition of dry plant roots was examined. The following remarks are summarizing the obtained results: 1) total chemical composition of dry plant root material from okra was higher than cucumber and eggplant. 2) the total number of soil fauna collected from okra was (3799 indiv. /10 traps) decreased to (3312 &2220 /10 traps) in cucumber and eggplant, respectively. 3) These results show that root type and its chemical composition may affect the increase or decrease of soil fauna.