Dr. Michael M. Baden was ordered dismissed today as chief deputy medical examiner of Suffolk County after a magazine quoted him as giving what the County Executive called ''advice on how to kill people.''

The County Executive, Peter F. Cohalan, said he had the authority to dismiss Dr. Baden because the forensic pathologist had not yet been permanently appointed. Dr. Baden has held the $53,557-a-year post for less than a year.

But Dr. Baden was not formally dismissed today because county aides said they needed time to check Civil Service laws and decide whether a public hearing must be held or written charges filed in conjunction with the removal.

Dr. Baden denied late this evening that he had been interviewed by Oui magazine, in which the article appeared, or that he had said what was attributed to him. ''Those quotes attributed to me just aren't what I said,'' Dr. Baden said. ''I didn't say anything about how to commit the perfect murder.''