This paper addresses the application requirements for the brightness temperature calibration of the hot calibration target for spaceborne microwave radiometers. Based on the temperature gradient characteristics of the absorbing coating of the calibration target and the mechanism of brightness temperature deviation, combined with practical temperature measurement methods and experimental means, a brightness temperature metrological calibration technology solution applicable for in-orbit use is studied. Given the current background of high emissivity design and determination technology of the calibration target being basically perfected, the paper focuses on summarizing the methods for determining the temperature gradient characteristics of the calibration target coating. The goal is to construct an in-orbit available brightness temperature calibration method that uses multiple parameters, such as the temperature measurements of the metal inner cone of the calibration target and the temperature measurements near the radiation aperture of the calibration target. Based on feasible electromagnetic simulation technology, thermal simulation technology, platinum resistance and infrared temperature measurement techniques, the paper preliminarily summarizes the implementation path of the brightness temperature calibration technology system for spaceborne calibration targets. This involves first constructing a basic brightness temperature calibration model considering uniform background brightness temperature and improving the mapping relationship from the inner cone temperature of the calibration target and the equivalent background brightness temperature to the longitudinal temperature gradient of the coating. Subsequently, an application model for brightness temperature calibration considering the installation environment is constructed, improving the mapping relationship from the temperature measurements of the inner cone and the radiation aperture area of the calibration target to the brightness temperature deviation of the calibration target. Finally, the validation and application of the brightness temperature calibration model are discussed.This work serves as an important technical basis and reference for further improving the accuracy of the calibration target's brightness temperature and even developing space microwave radiometric measurement benchmarks.