A quantitative phase field method of multi-component diffusion-controlled phase transformations coupled with the Kim-Kim-Suzuki model was applied to study the effect of initial particle size distribution (PSD) in 3D and space distribution in 2D on dissolution of α particles in Ti-6Al-4V alloy below β transus temperature in real time and length scale.The thermodynamic and mobility data were obtained from Thermo-Calc and DICTRA softwares,respectively.The results show that the volume fractions of α particles decay with time as:f =feq + (f0-feq) exp(-Ktn) for four cases of PSD.The sequence of dissolution kinetics from fast to slow is:uniform PSD,normal PSD,lognormal PSD and bimodal PSD.The space distribution is found to be a major factor affecting the dissolution kinetics and the microstructures.When the distance of the particles is less than critical value,the dissolution rates reduce with the decrease in distance.The Al and V concentration fields around the particles appear more obvious soft impingement.