The purpose of this study was to the observe effects of the various bleaching agents on blood clot. Absorbent papers(N9.5) were coated with O type blood and were dried in shadow for 72 hours. Bleaching agents used were 5% NaOCl 30% $H_2O_2$, saturated solutions of $NaBO_3$ $4H_2O$, $Ca(OCl)_2$ and $Na_2O_2$ at $20^{circ}C$. After the specimens, blood cloted papers were dipped in 10CC of solution for 1 minute, 5 minutes, 30 minutes, 2 hours and 24 hours, specimens were washed with distilled water and dried. Hue Value/Chroma contrived by Munsell was measured in each specimen. The following results were obtained. 1. Superoxol changes 2.5YR 4.5/2 into N9.5 (white) after 24 hours. 2. All bleaching agents except superoxol change YR into Y.