A principle study of detecting laser frequency signals based on edge technology for atmospheric laser communications is presented. An experimental system is built up in which an iodine cell is used as the edge filter. The experimental results were analyzed in detail. Applying edge technology the communication system has two main advantages, the narrow optical bandwidth and the high stability of laser frequency. So an ultra narrow optical filter with bandwidth about 400MHz can be used in the receiver. The receiver is only sensitive to the frequencies of the laser signals. Most of the interference of background light field can be eliminated. Some problems exposed in the experiments are discussed.