Abstract: A standard audit manual (SAM) rating matrix system includes a rating matrix model established base upon a standard audit manual by evaluating of internal controls to determine an internal control rating value, appraising a likelihood of potential errors and material misstatement to determine an error rating value, appraising a professional risk to determine a risk rating value, and appraising a materiality guideline to determine a guideline rating value. Therefore, an audit rating value is evaluated in accordance with said rating matrix model to implicate a level of likelihood of errors and a risk level of misstatement so as to derive an overall assessment and evaluation and forms bases of formulating an audit approach for each audit engagement.