Internal reference thought of supervision by public opinion is important part of CPC’s thought of supervision by public opinion. CPC’s internal reference thought of supervision by public opinion has matured gradually in decades of development from publishing internal issues to internal reference, to establishing and improving internal reference communication mechanism, then to becoming important channel of supervision by public opinion. Theoretically and practically, this thought consists of four aspects: internal reference should accept the leadership and supervision of the Party, internal reports strictly distinguished from public reports, internal writing be more cautious, and internal communication be strictly rated and kept in secret.