According to the poor heat exchange efficiency and low compact degree of traditional economizer used in boiler, a new type of plate economizer was developed. The heat-transfer mathematical model of the new plate economizer was established and its heat transfer characteristics were numerically solved by using Fluent 6.3. Then, the influence of the channel shape and flow characteristics of flue gas and water on the heat transfer effect and flow resistance are discussed, as well as the heat transfer effect between plate economizer and fin-and-tube economizer is compared. The results show that the heat transfer coefficient of plate economizer is higher than that of fin-and-tube economizer under the same conditions. The heat transfer effect of plate economizer can be improved by adding bulge in flue gas channel, which is 51% more than that of fin-and-tube economizer. Compared with traditional economizers in power plants, new plate economizers will increase heat transfer efficiency and reduce energy consumption.