Objective To investigate the difference between invasive and non-invasive blood pres-sure monitoring for patients after mechanic valve replacement. Methods Invasive or non- invasive blood pressure of 40 patients after mechanic valve replacement were continuously monitored for 24 hours, and the results underwent t test. Results There was a significant difference between invasive and non-invasive blood pressure monitoring for patients within 12 hours after mechanic valve replacement, but no difference was seen between them after 12 hours. Conclusions It can provide more accurate bases by monitoring blood pressure invasively at early stage after mechanic valve replacement, and it can be replaced by non-invasive blood pressure monitoring 12 hours after mechanic valve replacement.