Two field experiments were conducted during the two successive winter seasons of 2012/2013 and 2013/2014 at Al-Bramoon Experimental Farm, Hort. Res. Institute, El-Dakahlia Governorate to study the effect of Silicate dissolved bacteria (SDB) and Thiobacillus Bacteria (TB) inoculation with different rates of potassium and sulfur fertilization on plant growth, yield and chemical constituents of garlic plants cv Sids-40. The used experimental design was split plot with three replicates. Potassium and sulfur fertilization represented the main plots at rates of 50, 75 and 100 % from the recommended dose, and the subplots were assigned to Silicate and Thiobacillus Bacteria either single or combined inoculation. Results showed that application of potassium and sulfur(100% rates of  K + S ) had significant enhancing effect on garlic plant growth parameters (plant height, bulb diameter/plant, leaves number/plant, fresh and dry weight/plant and total chlorophyll SPAD unit). In addition, yield and yield components(i.e. total yield/fed, fresh weight/bulb, average clove weight and number of cloves/bulb) significantly increased by this treatment. Chemical constituents also was significantly increased by application of this treatment, in addition N%, P%,K% and volatile oils in garlic cloves were increased by this treatment in compared with other treatments. On the other hand, inoculation with SDB + TB significantly increased all above parameters of plant growth, yield and chemical constituents as compared with other treatments. The combined treatment of K+S at rates of 100% with SDB and TB inoculation was the optimum treatment for improving the produced yield (72.27 and 64.22 % increment in the first and second seasons, respectively comparing to the control treatment). Therefore, the treatment (100 % K+S) with (SDB + TB) could be recommended for raising garlic yield and improving bulb quality under similar conditions to this work.