Physicists and historians of science all consider that the observable principle was very important for creating quantum mechanics. Following the publication of Heisenberg’s “one person paper”in 1925，most of thebooks and papers related to the history of quantum mechanics have indicated that the observable principle was a great contribution from Heisenberg. In fact Heisenberg was not the physicist who first presented observablity. Max Born had already clear described the idea in his book published in 1920，and he also repeated it frequently to Landé when he was the professor in Frankfurt，from 1919 to earlier 1921. A lot of evidence could prove that Heisenberg learned the observable principle from Gttingen，directly from professor Max Born.