A noise removal method and system using a change in activity pattern, in which it is recognized that noise components exist in different frequency bands and different filters for removing noise are stored according to each activity pattern, thereby optimally removing the noise components. A method of removing noise by using a change in an activity pattern includes: recognizing an activity pattern of the subject using an activity sensor; sensing a first bio signal corresponding to the activity pattern from the subject using an electric potential sensor; recognizing a noise generation pattern according to the activity pattern by analyzing a noise component for each section of the first bio signal; selecting filter information for each section according to the noise generation pattern; storing the filter information selected for each section in association with the activity pattern; and removing noise from a second bio signal sensed from the subject by applying the stored filter information.