Abstract: The present study was aimed at to develop a Phosphate Solubilizing Bacteria’s (PSB) inoculum for improving Phosphate (P) uptake on phosphate sludge. Twelve PSB were isolated from three types of rhizosphere soil from Chennai, India were studied for phosphate solubilization on Pikovskaya’s medium. Isolates were subjected and studied for Solubilization Index (SI) for selecting the high efficient strain. In results, the PB08 strain exhibited high SI 4.80 at sixth day incubation and it was grown in vitro for ten days in Pikovskaya’s broth containing 1% tricalcium phosphate (TCP) and 1% Phosphate Sludge (PS). Variation occurs in phosphate solubilization of two media which contain two P source inoculated by the same strain (PB08). Unlike SI and pH drop, fluctuations in phosphate solubilization were observed during 10 days and gradual increase in phosphate solubilization was noted. Values of solubilized tricalcium phosphate ranged from 9.6 to 136 ppm. The results emphasize that the PB08 may be used for inoculum production and their inoculation effect on plant growth can be studied in vivo.