We think that estimation of acoustic cavitation generated in frequency range of MHz is important for safety assessment of ultrasound exposure to human body and tissue. The objective of this paper is to measure the generated active oxygen together with acoustic cavitation by using special acoustic cell and KI oxidation dosimetry at focal point in 1.6 MHz focused ultrasound field and to research relationships between ultrasound exposure condition and the amount of generated active oxygen. We will report experimented results about the duty cycles of ultrasound burst vs. change in peak absorbance at 350 nm that represent color reaction of 13 ion caused by ultrasound exposure. The peak absorbance near 350 nm increased in proportion to duty cycles between 30 and 100 %. However, when the duty cycle is 50, 80 and 90 %, increasing tendency of absorbance saturated. To investigate this cause, we researched about relationship among the temperature of the transducer increased with increase of duty cycles, the dissolved oxygen level in water tank with KI solusion and the generated active oxygen. We will report about these experiments and their results.