The Communist Party of China owns the qualities of facing the reality, advancing with the times, self- criticism and self- correction.“ The Letter in Sept.” corrected the underestimate of the situations the Red Army soldiers were facing in and the mistakes in the guidelines and policies for the construction of the Party and the Army in the Red Army in“ the Letter in Feb.” , and it promoted the process of the Chinese revolution. The Central Committee of CPC adjusted the policies in only half a year according to the changes of situations, which just showed the good qualities of the Party. In the construction of socialism in the new age, the Party should carry on these qualities to push forward the construction progress of a well- off society.