We have studied the influence of ferric iron on the production of siderophore (microbial iron transport compound) from Pseudomonas sp. on universal CAS (Chrome azroul S) assay agar and modified sugar-aspartic acid (MSA) agar or liquid medium respectively. The results showed that the non-fluorescent siderophores (pyochelin) were produced on universal CAS assay agar and liquid medium and fluorescent siderophores (pyoverdine) on MSA agar and liquid medium; and the pyoverdine was more sensitive to the response of ferric iron whatever on agar plate or in liquid medium.