Abstract: Aim of this studies, to improve phosphate solubilization activity of Penicillium citrinum at different salinity condition, carbon sources and varying level of pH. Plant Growth Promoting Fungus (PGPF) isolated from rhizosphere of sugarcane and identified as Penicillium citrinum Thom. was tested for its phosphate solubilizing ability on four carbon sources viz., glucose, sucrose, glycerol and mannitol, sources of salinity viz., NaCl, CaCl2 and KCl at varying range of reaction (pH) in vitro condition. Among the carbon sources, Penicillium citrinum Thom. was found to be maximum significant solubilization of tricalcium phosphate (461 μg mL-1) in presence of glucose as carbon source, while minimum phosphate solubilization (421 μg mL-1) in presence of sucrose. Further, the effect of different salinity (NaCl, CaCl2 and KCl) was tested at different pH (6.0, 7.0 and 8.0) under in vitro condition. Presence of 1% CaCl2 at pH 8 in broth culture was maximum solubilization of tricalcium phosphate (455 μg mL-1) than other salt concentration (NaCl and KCl) by this fungal strain of P. citrinum Thom. Results of this studies was found suitable carbon source as glucose for more solubilization of tricalcium phosphate. Also salinity effect on solubilization of tricalcium phosphate by P. citrinum was showed maximum significant in 1% CaCl2 at pH 8.0. This finding can provide great benefit in the maintaining the available phosphates for crops in saline and alkaline soils. A large fraction of land arid and semiarid regions is affected by salinity in India. About 7.5 million of hectares of land are saline or alkaline, which is improved by Penicillium citrinum.