Abstract: The present invention provides a test strip and a detecting method thereof. The test strip comprises a first sheet, a second sheet a first filter and a second filter. The first sheet comprises a bulge portion deposited substantially in the center thereof. The second sheet comprises a depression in alignment with the bulge portion to form a sealing space. The first filter is disk-shaped and deposited in the sealing space. The first filter is used to receive a biological sample. The second filter is ring shaped and disposed in the sealing space and under the first filter to receive the biological sample coming from the first filter. The first filter comprises sodium azide, sodium dihydrogen phosphate, and urea, and the second filter comprises sodium azide, phenol red, and urea.