For cultivation mushroom (Pleurotus ostreatus) four agro-industrial wastes namely Rice straw (RS) , sawdust (SD) , waste paper (WP) and cardboard industrial (CI) were used. Molasses (M) can be used as a main energy source and addition of 5% molasses fo the substrates to improve the mushroom growth, yield and biological efficiency. Results regarding to the time required for completion of spawn running, pinheads and fruiting bodies formation. The spawn running, pinheads and fruiting bodies formation were found within the period ranged from 12 to 25. from 22 to 52 and from 25 to 55 days respectively. When added molasses to the substrates the spawn running, pinheads and fruiting bodies formation were found within the period ranged from 10 to 22, from 20 to 47 and from 24 to 52days respectively. The rice straw  treatment containing 5% molasses gave the maximum mushroom yield (717.5 g per 1 kg dry substrate). Waste paper (WP) gave minimum mushroom yield (112.14g). The highest percentage of biological efficiency was obtained on molasses rice straw treatment 71.75 %. Low percentage of biological efficiency were found in WP (11.21%). Molasses significantly increased the biological efficiency over control substrates.