Due to the adverse effects of conventional chelating agents, such as ethylenediaminetetraacetic acid (EDTA), on the environment, the use of biodegradable alternative chelating agents in various industries has been considered today. In this study, the effect of new chelating agents, methylglycinediacetic acid (MGDA) and L-glutamic acid N,Ndiacetic (GLDA) were compared with those of EDTA on soil biological parameters, in a completely randomized design with a factorial arrangement and three replications. The ligands were applied to the soil at nine levels (2, 4, 6, 8, 10, 15, 20, 30.50 mmol/kg soil) and incubated for 12 and 40 days. At the end of the incubation times, some soil microbial parameters, including basal respiration, substrate-induced respiration, arginine ammonification, microbial biomass, and metabolic quotient were measured in the soil samples. The results showed that EDTA and GLDA had no significant effects on substrate-induced respiration, arginine ammonification, and microbial biomass, but they increased basal respiration and metabolic quotient indices in the 12-day incubation period. However, MGDA significantly increased all biological parameters studied over the same period compared to the control. These results were mainly observed over the 40 days as well, except that EDTA and GLDA also increased substrate-induced respiration compared to the control. Overall, the results of this study showed that low concentrations (less than 15 mmol/kg) of all three chelators did not negatively affect the soil biological indices and even promoted some indices. However, at high concentrations (especially 50 mmol/kg soil) the effect of these chelators was undesirable on biological properties of the soil. Key words : EDTA, MGDA, GLDA, Soil pollution, basal respiration, substrate induced respiration, arginine ammonification, microbial biomass, metabolic quotient.