Hi EmployeeOcta,
1. Create a new team (say, Admin Users Team)
2. Add only the users who supposed to run the particular reports to this Admin Users Team. In future, if you need to allow any non-system admin users to run the reports, you can just add them to this team
3. Assign a security role (you can create a one) which has minimum read access to Report entity
4. Under Administration tab of the reports you wanted to display only to the admin users, set Viewable By to Individual and Owner to 'Admin Users Team'
4. Security Roles expect System Administrator and the one created at step #3, should not have org level permission on report entity
Update: I just realized that Wahaj Rashid's answer also correct. All the users with system admin role can see the report. But you need to ensure no other roles having org level read permission on Report.
