The invention relates to a line temperature identification method for dynamic capacity expansion of a power transmission line. The method includes: obtaining on-line monitoring data of the power transmission line, converting the data to monitoring data in a CIM/E format that follow the IEC61970 standard, and storing the monitoring data in an internal storage, wherein the monitoring data in the CIM/E format include control parameters and monitoring information; preprocessing the monitoring data in the CIM/E format; building a wire temperature identification model, and identifying the preprocessed monitoring data in the CIM/E format; thereby improving credibility of the monitoring information of the power transmission line, and improving the transmission capacity of the power transmission line on the premise of ensuring stable operation of a system and equipment safety.