Background: According to the importance of Stevia rebaudiana that it’s sweetener steviol glycosides, has been introduced in recent year as a natural alternative for saccharose, the evaluation of bio-fertilizers effects on growth and development of stevia is necessary.

Objective: In this research the effect of vermicompost and mycorrhiza on growth traits and steviosid (ST) content in Stevia rebaudiana was studied.

Methods: This research was conducted in faculty of agriculture of Tarbiat Modarres University, Tehran, Iran, through a factorial experiment based on randomized complete block design with 12 treatments and 3 replications. The first factor was different levels of vermicompost (0, 10% and 20%) in basal medium including garden soil + 15% by weight Cow manure and also garden soil alone as a control treatment. Second factor was mycorrhiza fungi including inoculation Glomus mosseae and Piriformospora indica and treatment of non-inoculated plants.

Results: The bio-fertilizers had significant effect (P≤0.01) on the studied parameters. The maximum amount of growth parameters (chlorophyll content, and fresh and dry weight of aerial parts and root) was obtained treatment of 20% of vermicompost and Glomus mosseae inoculation. The highest content of steviosid was obtained in end of vegetative growth stage and control treatment.

Conclusion: Application of vermicompost significantly improved the chlorophyll content and growth traits and also the highest their amounts were obtained in combination treatment of vermicompost and mycorrhizal inoculation.