A strong and stable room temperature phosphorescence (RTP) signal of phenanthrine aqueous solution in the absence of a protecting medium can be induced only by using Na2SO3 as deoxygenator and KI as heavy atom pertuber. The maximum phosphorescence intensity wavelengths are lambda ex/lambda em = 283/482,504 nm. It is also found that the kind and amount of organic solvent added to the luminescent system effects obviously the RTP properties. Under the present of 1% acetonitrile the RTP intensity is linear to phenanthrine concentration in the rage of 8.0 x 10(-7)-6.0 x 10(-6) mol.L-1 and 6.0 x 10(-6) mol.L(-1)-4.0 x 10(-5) mol.L-1, respectively. The detection limit is 2.6 x 10(-8) mol.L-1.