The effect of trace boron on phase transition temperature, specific heat, surface tension, fluidity and microporosity of K4169 superalloy has been investigated. The influence of different contents of minor element boron on liquidity of K4169 superalloy and quantitative measurement of the area percentage of microporosity were also studied by two different fluidity models of superalloy designed by ourselves. The results show that when the content of boron increases from 26 mg/kg to 59 mg/kg, the fluidity of K4169 superalloy can be greatly improved; however, the percentage of microporosity decreases and then increases. When the content of boron reaches 59 mg/kg, the microporosity is the smallest. Solidification parameters were measured by differential scanning calorimeter (DSC). The results indicate that with the increasing of boron content the solidification range becomes narrow, while when the content of boron exceeds 59 mg/kg, the solidification range increases. JMatPro software calculation results show that with the increasing of boron content, the surface tension of the alloy is gradually reduced. EDS analysis reveals that when the content of boron reaches 70 mg/kg, boride will precipitate in the superalloy.