According to the criterion of micro-ex- plosion occurrence, a new viewpoint that micro-ex- plosion may not occur in diesel engines is presented in this paper. The relationship among the diameter change of an emulsified fuel droplet, water and fuel evaporation rate is obtained from the multi-compo- nent control equations of the droplets. Because the evaporation rate of water is much more rapid than that of fuel, water will evaporate much quickly than fuel in this process, so the water is evaporated in advance, and at the same time large droplets change into small ones. This is in fact the main reason of combustion intensification for emulsified fuel. The investigators at home should notice that the fuel droplets used in the previous experiments were al- ways droplets with big diameter (about d0≥250 μm), which might be owing to the restriction of the ex- perimental conditions. Micro-explosion does hap- pen on such fuel droplets with big diameters, which has caused all the authors to think that micro-explo- sion would happen on all the droplets without excep- tion. However, it cannot be used to explain what really happens in diesel engines. In our research, we have found that micro-explosion will not occur when the size of droplets is too small, and the same is case with diesel engines. According to the criterion of micro-ex- plosion occurrence, a new viewpoint that micro-ex- plosion may not occur in diesel engines is presented in this paper. The relationship among the diameter change of an emulsified fuel droplet, water and fuel evaporation rate because the evaporation rate of water is much more rapid than that of fuel, water will evaporate much faster than fuel in this process, so the water is evaporated in advance, and This is the same reason large droplets change into small ones. This is in fact the main reason of combustion intensification for emulsified fuel. The investigators at home should notice that the fuel droplets used in the previous experiments were al- ways droplets with big diameter (about dO ≧ 250 μm), which might be due to the restriction of the ex-perimental conditions. Micro-explosion does hap-pen on such fuel droplets with big diameters, which has all the authors to t hink that micro-explo- sion would happen on all the droplets without excep- tion. However, it can not be used to explain what really happens in diesel engines. In our research, we have found that micro-explosion will not occur when the size of droplets is too small, and the same is case with diesel engines.