A welding temperature field control system. An output end of a Dahlin controller is connected to a welding power supply of a welding machine system, and a welding pool temperature measurement unit transmits detected welding pool data to a collected signal input end of the Dahlin controller. A welding temperature field control method. The method comprises: divide a weld seam and heat effect zone into three welding zones, namely, a high-temperature welding zone, a medium-temperature welding zone and a low-temperature welding zone; a welding pool temperature measurement unit acquires images of heat radiation fields of two wave bands on the back sides of the welding zones by means of a CCD camera; carry out filtering on the collected images of the heat radiation fields to obtain a correspondence between gray scale values and temperatures; obtain distribution of a whole welding temperature field according to the correspondence; calculate the width of an isotherm; and a Dahlin controller outputs a control value to a welding power supply of a welding machine system. By means of the welding temperature field control system and method, closed-loop control over the width of the isotherm of the back side of a weld seam and heat effect zone is implemented, residual errors in automatic welding objects are eliminated, the production efficiency is improved, costs are reduced, and rapid, accurate and convenient detection and quality control are implemented.