This invention discloses a method for extracting lithium from carbonate clay type lithium ore based on ion exchange, which belongs to the field of lithium extraction technologies. This method aims to, with iron salt as the extractant, extract lithium into the solution through exchange reaction with lithium ore, which mainly involves the following steps: have clay type lithium ores crushed and ground prior to high-temperature roasting activation, and then conduct iron exchange reaction by iron salt solution while heating, followed by solid-liquid separation by means of filtration. The filtrate obtained will be lithium-bearing solution, and the extraction rate of lithium can reach as high as over 90%.