The explosion characteristics of vapor-liquid two-phase n-heptane inside and outside (the boundary is the junction of premixed fuel and air) the original premixed zone studied, and the effects of concentration and initial temperature on the explosion development have been analyzed using a numerical method. The explosion overpressure increases with distance in a certain range outside the premixed zone with the change of premixed vapor-liquid two-phase n-heptane concentrations. The peak overpressure of rich fuel is larger than that of lean and stoichiometric fuel. The fuel rich explosion outside the premixed zone results in a so-called secondary explosion, and the explosion overpressure has two peaks with similar values. The initial temperature has a significant effect on the flame length (characterization by combustion rate) of two-phase n-heptane explosion. The flame length of a lean fuel explosion decreases with the increase of initial temperature. At an initial temperature of 253 K, the flame length is 4.15 times that of the premixed zone. With stoichiometric and rich fuel, the flame length increases with the initial temperature in the range of 273-333 K, and at 333 K the flame length is 5.26 and 5.99 times that of the premixed zone, respectively. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.