In this investigation, the critical emitting heat flux was measured and analyzed corresponding to a liquid explosive emission phenomenon occurring in a capillary tube, as well as the temperature outside tube wall. The asymmetrical distribution of two nonheated side sections of the tube had a significant effect on the explosive emission. Two dimensionless parameters, geometrical and thermal asymmetry, and the asymmetrical function were introduced to describe the general asymmetrical effect based on the experimental results of tubes with different tube inner diameters, heating length, and heating systems. For a larger thermal asymmetry, the critical emitting heat flux decreased significantly as geometrical asymmetry became larger. For a smaller thermal asymmetry, geometrical asymmetry has a little effect on the critical emitting heat flux.