The invention relates to a power transmission line dynamic capacity-increase system based on a wire inclination angle. The power transmission line dynamic capacity-increase system is technically characterized by being composed of a plurality of data collection terminals and a monitoring platform, each data collection terminal comprises a sensor, a conditioning circuit of the sensor, a CT electricity supply module, a main control module and a wireless data transmission module, each sensor is connected with the corresponding signal conditioning circuit, the output end of each signal conditioning circuit is connected to the corresponding main control unit, each CT electricity supply module supplies power to the corresponding main control module, each main control module is connected with the corresponding wireless data transmission module, and the wireless data transmission modules are connected with the monitoring platform through RF antennas. The power transmission line dynamic capacity-increase system solves the problems that a primary side tension meter is hard to install and the wind speed and direction measurement is not accurate on the basis of the design of power transmission line running parameters including the inclination angle, the environment temperature, the solar radiation and the wire load and by calculating the dynamitic carrying capacity of a wire according to the wire temperature, the environment temperature, the solar radiation and the wire load, and the power transmission line dynamic capacity-increase system has the advantages of being safe in temperature measurement work, easy and convenient to install and maintain, high in reliability and safety, and the like.