Abstract: Parallel comparison of GPSO3 (made in China) and Vaisala (made in Finland) ozonesondes was carried out at Atmospheric Observing Experimental Base, CMA, in Beijing during the period of Jan 11—23, 2002, 7 pairs of ozonesondes were launched. Comparison results show a relative good consistence in the ozone vertical variation characteristics obtained by both type of ozonesondes in general. The average relative error between ozone concentrations at 12—27 km in the atmosphere measured by the both type ozonesondes is less than 10%, while at altitudes below 12 km and above 27 km, the measured ozone concentration by GPSO3 sonde is higher than that by the Vaisala one. Comparison method is introduced, comparison results of some ozone variation futures are analyzed, a possible influence of sonde ascending speeds during soundings on the comparison results is discussed as well.