Plasma is the spectral source of laser-induced breakdown spectroscopy (LIBS), and the distribution of its internal species will directly affect the signal-to-noise ratio of the collected emission lines. Therefore, research on the species distribution of vapor plasma is of great importance for improving the quantitative performance of LIBS. In this paper, the laser-induced plasmas on the surface of binary Al-Sn alloy are analyzed using spectrally, spatially and temporally resolved dual-wavelength differential imaging to obtain the emissivity images of species and explore the species distribution and evolutionary mechanism of plasmas with different laser supported absorption wave (LSAW) regime. The laser-supported combustion wave (LSCW) and laser-supported detonation wave (LSDW) dominated plasmas are induced using low and high-irradiance laser pulses, respectively. The interactions between laser, alloy and plasma are analyzed by observing the morphology, species distribution, species lifetime and internal structure of the plasma, and combining with the physical properties of elements and spectral transition structure, the space-time evolutionary mechanisms of the binary laser plasma are formed. From our observation of the emissivity images of species, we can conclude that: (1) laser irradiance can change the species distribution of plasma; (2) the LSCW-dominated plasma has an obvious layer structure, and the absorption zone of laser energy mainly located in vapor plasma. The species’ lifetime is relatively short, and the species distribution mainly depends on the melting points of constituted elements in the sample. The element with a lower melting point will melt faster and distribute in the top of vapor plasma; (3) The propagation model of plasma induced by high irradiance laser is LSDW. A large mixing region between the vapor plasma and the shocked gas layer can be observed, and the main absorption zone of laser energy is the shocked gas layer. The lifetime of species in plasma is prolonged, and the species distribution mainly depends on the atomic masses of elements. At this point, the species in the ablation zone of high laser irradiance on the surface of immiscible alloy will vaporize at the same time, and the velocity of the species is inversely proportional to the square root of the relative atomic mass. The species with smaller atomic mass move faster and distribute at the top of the vapor plasma. The above behaviors on species distribution in binary plasma are expected to be suitable for other elements or multi-element plasmas.