Among them can be raised in many research works of different authors related to the quality of audit activities and the factors affecting the quality of the audit, such as studies of DeAngelo 1999 ,Francis and Al 1987 1988 1999 on audit fees; Burton's research 1990, Malone and Roberts 1996, Wooten 2003,Chen 2009 on matters related to the auditors, the study by Tran TG Tan 2009,K Tran Lam 2011, Ha Ha TN 2011 on control audit quality frim inside and outside corporate auditor;