You may apply for Canadian citizenship if you have lived in Canada as a refugee, but only if you have since become a permanent resident (PR) and meet all the other citizenship requirements.
Time spent in Canada as a protected person or refugee claimant does not count toward the physical presence requirement for citizenship. However, once you receive permanent resident status, each day you spend in Canada counts as a full day toward the 1,095-day (3-year) residency requirement within the last five years.
In addition to meeting the physical presence requirement, you must also file taxes (if required), demonstrate language proficiency if you are between 18 and 54, and pass the citizenship test if applicable.
If you are unsure whether your time in Canada qualifies, use the Physical Presence Calculator to check your eligibility before applying.