To studing the effects of two planting substrates on vegetative growth, reproductive growth and antioxidant activities of four bell pepper ( Capsicum annum L.) cultivars, a greenhouse 4×2 factorial experiment was conducted in a completely randomized design with 4 replications in greenhouse of Department of Horticulture of Isfahan University of Technology. First factor was the bed of 80% cocopeat + 20% perlite and 80% moeat + 20% perlite and the second factor was four bell pepper cultivars consisted of green ?Traviata?, red ?Iratian?, orange ?Aracia? and yellow ?Taranto?. Seedlings were planted in 7-liter pots that were filled with planting substrates. Irrigation and nutrition were done by using drip irrigation system and Johnson ? s nutrition solution (0.5 concentration), respectively. Date of first flowering bud opening was recorded and flowering rate was calculated. Fruits were harvested in the stage of three quarters of color change and the length, diameter, number of lobes, firmness, pericarp thickness, titratable acidity, total soluble solids and vitamin C of them were measured. The number and weight of fruits for calculating yield were recorded. Plants were removed from pots five month after tralanting and vegetative growth factors consisted of length of stem, diameter of stem from third node, number of nodes, relative chlorophyll content, fresh and dry weight of stem, length of roots, fresh and dry weight of roots were measured. The methanol extract of fruits were prepared and then extract yield, total phenolic compound by using Folin-Ciocalteau reagent, DPPH free radicals scavenging and OH ° scavenging were measured. Results showed that moeat caused better results on vegetative growth consisted of length of stem, diameter of stem, relative chlorophyll, fresh and dry weight of root and stem and reproductive factors consist of flowering rate, fruit length and diameter, fruit shape index, fruit firmness and pericarp thickness and it increased fruit number and fresh and dry weight of fruits in each plant in comparison to cocopeat. Planting in moeat also increased antioxidant activities consisted of total phenolic compounds, DPPH free radicals scavenging and OH ° scavenging. Between different cultivars red cultivar was performed better characteristics such as more relative chlorophyll, fresh and dry plant weight, fruit shape index, pericarp thickness, vitamin C content and antioxidant activities compared with other cultivars. There was significant interactions between bed and cultivar, so that effects of beds for some traits were depends on cultivars. Key words: Bell pepper cultivars, Cocopeat, Growing substrate, Moeat