Tentative study on the flash ultraviolet generator for high- speed microscopy in the atmosphere is described. The ultraviolet generator for fundamental studies consists of the following essential components: a high-voltage generator, a high-voltage main condenser, a thyratron, and a mercury-xenon lamp. The high-voltage condenser is charged up to about 14 kV, and the electric charges in the condenser are discharged to the lamp by closing the thyratron. The flash ultraviolet rays including visible lights are then produced. The radiation intensity increased according to increases in the electrostatic energy in the condenser by increasing the condenser charging voltage. The cathode voltage (- 1 times the tube voltage) and the discharge current were measured by a high-voltage divider and a current transformer, respectively. The peak cathode voltage increased according to increases in the charging voltage, and the value with a charging voltage 14 kV was about -14 kV. When the charging voltage was increased, the tube current increased, and the peak current had a value of less than 0.35 A. The output of ultraviolet rays including visible lights was detected by a pin diode, and the duration was less than 1 microsecond.