In the past decade, mass spectrometry (MS) has been widely used for a broad range of on-site applications. This is largely attributed to the rapid advancement of technologies, such as ambient ionization and mass spectrometer miniaturization. Here, we report the development of the temperature-tuning desorption ionization (TTDI) method for versatile on-site applications using a miniature MS system. A unique feature of TTDI is its dynamic temperature range applicable from 30 to 800 °C, which enables optimal desorption ionization applied for chemical and biological compounds through tuning the temperature at the sampling spot. The versatility of TTDI has been demonstrated through on-site MS analysis of a variety of samples, such as explosives on surfaces, drugs of abuse in biofluids, and screening biomarkers in tissues.