The invention provides a method and a device for realizing on-line analysis on simulated combustion of cigarettes by using a thermogravimetric analyzer and a GC/MS and is characterized in that: the method comprises the following steps of: putting a cigarette sample in the thermogravimetric analyzer for programmable temperature rise cracking under a condition of inert gas or synthetic air, and sending thermal cracking products to a six-way valve by a controllable temperature transmission line; simultaneously, according to experimental requirements, selectively sending the cracking products at different temperature stages to a PTV sample injection opening by the six-way valve, separating the cracking products enriched by condensation of liquid nitrogen by the gas chromatography GC, and delivering the cracking products to the mass spectrometry for quantitative and qualitative analysis; and simulating conditions of the combustion of cigarettes, completing cracking experiments of gram-class cigarette samples at different temperature-rise speed and with different oxygen contents.