Density data of carbon dioxide (CO(2)) + brine solution from Tianjin reservoir were determined using magnetic suspension balance (MSB). Measurements were performed in the pressure range (10 to 18) MPa and at the temperatures (313 to 353) K. CO(2) mass fraction in solution was selected up to 0.040. The experimental results revealed that the density of CO(2) + brine solution decreases with increasing temperature and increase with increasing pressure. The density of CO(2) + brine solution increases almost linearly with increasing mass fraction of CO(2) in solution. The slope of the density vs CO(2) mass fraction curves decreased from 0.222 to 0.185 as temperature increased from 313 to 353 K and is independent of pressure. Two regression functions were developed to describe the density data of CO(2)-free brine and CO(2) + brine solution from Tianjin reservoir under sequestration conditions, and the errors between experimental results and prediction were within 0.004% and 0.03%, respectively.