Based on Alexander’s theoretical crushing model and empirical Cowper-Symonds equation, a formula including strain rate effect for predicting dynamic mean crushing force of circular tube was derived, and derivation differences between the above and theoretical formulas put forward by Abramowicz were discussed. Then it adopted the drop tower rig to make the impact test for 9 kinds of Q235B longitudinally thin-walled welded tubes, and the test results were compared with the theoretical prediction values. The result comparison shows that the predicting formula of dynamic mean crushing force derived from Alexander’s model gives lower results, and Abramowicz’s formulas give bigger results. At last, referring to impact test conditions and results, it modifies the Abramowicz’s formula by setting sensitivity coefficient of strain rate from 3.91 to 3.0. The modified values correlate well with all test results and the maximum deviation is lower than 8%. In addition, it also proposes a simple dynamic peak crushing force formula for predicting thin-walled welded tubes with media sizes theoretically.