<p><strong><em>Background and Objectives:</em></strong> Treatment team perform a variety of practices in the fields of treatment and caring. The main domain of nursing practice is to prepare patients for diagnostic tests. Colonoscopy is a method of endoscopy of lower gastrointestinal system which needs proper colon preparation that allows proper assessment, diagnosis and positive treatment. Currently, there are different methods of bowel preparation. Therefore more research by a clinical nurse on this can result in better care. This study was aimed at comparing the routine method (caster oil and bisacodyl tablet) and oral sodium phosphate on the level of patients’ acceptance and bowel cleansing in patients undergoing colonoscopy.<strong><em>Methods</em>:</strong> The study was a one-blind controlled randomized clinical trial done on 90 outpatient candidates for colonoscopy referring to Razi Training Center in Rasht city. Samples were randomly chosen on the visit day and divided to 2 groups of experiment and control. Data collection instrument included a demographic questionnaire and checklist to assess the level of patients’ acceptance and bowel preparation. Primarily demographic data form for each patient was filled, and then intervention was done for two groups with 45 samples. During the process the acceptance form was filled by the researcher by asking the patient and also the check list on the residual stool score and global preparation assessment left was marked by colonoscopist and the nurse.<strong><em>Results:</em></strong> The findings indicated that patients’ acceptance (p&lt;0.000) and the level of bowel preparation (p&lt;0.000) was better with oral sodium phosphate.</p><p><strong><em>Conclusion:</em></strong> According to the results result oral sodium phosphate has better acceptance and is more effective on colon cleansing prior to colonoscopy when compared with routine regime (caster oil and bisacodyl tablet).</p>