Abstract: Oil and gas ascending velocity is one key parameter which not only reflects the energy information of the drilled layer but also directly influences well control safety and reservoir protection evaluation. There some problems with the present calculation methods which were uniform with some errors. It is necessary to settle the existing problems of uniform calculation and big problems between. In order to make sure of well control safety and original data accuracy, in this paper, some examples at well site were used to analyze the reason why errors happened during calculating the oil and gas upward flow velocity. By determining the key parameters of calculation, the particular improvement method and steps were put forward. After one year application to about fifty wells, great oil stimulation showed. The method can be used widely at the field.