In this paper, we first propose and demonstrate a novel tracing atom based absorption spectroscopy method for the real-time measurement of the temperature rise inside the pump region of a pulsed diode pumped alkali laser (DPAL). By artificially adding potassium atoms into the gain medium of an operational rubidium laser, the information of the temperature rise can be obtained from the variation of the potassium absorption signal. Some important influencing factors are studied. Typical results show that, as the pump power (2 ms duration) increases from 22 W to 92 W, the temperature rise increases from 103 K to 227 K. As the pulse duration increases from 1ms to 5 ms, the temperature rise increases from 128 K to 314 K, and the heat relaxation time increases from 3.8 ms to 8.1 ms. The method is favored for its ability for real-time detection and high sensitivity, which provides a useful way for DPAL diagnostics.