A simple, quick and nondestructive test method has been developed for determining Brassicaceae seed viability with single seed using resazurin reagent (RR) which was made by resazurin and yeast mixture. The color of the RR was changed from blue to pink or colorless when the aged seeds are soaked in the RR solution for 4 hours at $35^{circ}C$. Seed soaking system was developed using 96-well plate and absorbance of the RR was measured at 570 nm with a multi-plate reader. Radish (Raphanus sativus L.) seeds were artificially aged to create seven contrasting levels of viabilities. The relationships between the germination percentage of the radish seeds and the absorbance, and percentage of blue or colorless fractions of the soaked RR were appeared to have very high correlations in linear regression depending on the viability levels. The blue color fraction contained a high percentage of the normal seeds, while pink or colorless fraction contained high percentage of abnormal and dead seeds. Six lots of naturally aged Brassicaceae seeds were tested using the RR to observe an actual capability of quality assessment for intact seeds. A model equation has been developed for predicting germination percentage of the seeds by the color fractions of the soaked RR from the intact six Brassicaceae seed lots. The equation was found to have high prediction accuracy of 98.2%. This method is very quick and simple to use with a high accuracy for determining the quality of Brassicaceae seeds nondestructively.