There are three kinds of liquid petroleum marker which is extracted by the basic or acidic, and both developer. Korean marker, Unimark 1494 DB (marker) have been spectrophotometrically analysed by the determination of absorbance at 582 nm after base extraction by Unimark 1494 DB Developer C-5 (developer). Some blue dyes which have same reactive radical of marker and can be changed deep blue color in base developer extraction (BDE), may be increased absorbance at 582 nm, but dyes or markers which can be increased the absorbance, were not unclear. In this experiment, effects of three dyes or marker such as Orimax Green 151 (the mixture of CI Solvent Yellow 16 and CI Solvent Blue 70), quinizarin and Orimax Blue 2N (CI Solvent Blue 35), and two solvent such as topasol (P-250) and lubricant (P-8) on the absorbance were studied by HITACHI Recording Spectrophotometer U-3300. It shows that all of them increased absorbance at 582 nm after BDE. Absorbance at 582 nm can be showed 0.0544 by Orimax Green 151 at the concentration of 3.96 mg/l, quinizarin at the concentration of 1.38 mg/l, and Orimax Blue 2N at the concentration of 2.73 mg/l in the artificial petroleum (normal diesel oil: topasol: lubricant=2 : 4: 4), respectively. Absorbance, 0.0544 indicates that concentration of marker is 1.64 mg/l in the reference curves, respectively. And also these results can be showed that the artificial petroleum have about 10% cheep fuel such as kerosene which have marker (16.0 mg/l). Absorbance of P-250 was 0.01361-0.22842 depending upon the purchasing date, and that of P-8 was 0.05644. pH of developer was 14.83, and so this result indicates that Unimark 1494 DB is a base extractable petroleum marker, phenylazophenol (US Patent No. 5,252,106). In the BDE, the slight color of Orimax Blue 2N, Orimax Green 151 and quinizarin in artificial petroleum changed to deep bright blue color, respectively. These result indicate that the absorbance at 582 nm by BDE may be increased not only by azo, diazo, amine and ketone (anthraquinone, coumarin) dyes or markers, but also the contaminants of P-250 and P-8 which have same as reactive radical of dyes or markers.