Abstract: Nowadays, some observation stations cancel the artificial observation of evaporation (during time when there is no ice formation). They obtain this data from evaporation tank. In order to gain successional and comparative data, we should calculate the conversion coefficient between evaporation tank and artificial observation equipment. The author adopted interrelated coefficient, significant correlation test and the characteristic of distribution coefficient in order to get the distribution characteristic of evaporation tank and artificial equipment. Simultaneously, the author calculated the conversion coefficient, upper coefficient and analysis of dispersion. The results showed that the inter-annual variability was different due to evaporation measurement equipment. Only values of evaporation tank in spring season passed significance test, the evaporation value had a weak correlation with time. Artificial evaporating value was slightly larger during the spring and summer seasons, Kurtosis coefficient was slightly deviated from 0; the summer evaporation distributed in the median range obviously. In June, July, August, October, the conversion coefficient was smaller than that of any other time, upper coefficient tendency was similar with evaporation value tendency in months. Especially during the season without ice formation, there was a rising tendency of the conversion coefficient. In conclusion, the liner correlation was obvious in average monthly evaporation value during many years; it was a good way to carry out the evaporation conversion.