Abstract: The SPACE system integrated with the dynamic mixing algorithm provided an opportunity to generate amodel concrete with high volume f raction of aggregate. In this cont ribution , influences of fineness and volume f raction (φ= 40 %～70 %) of aggregates were studied on the nearest surface spacing dist ribution between neighboringaggregate grains in model mortar for three types of aggregate size dist ributions (one with the size range of 0.125～1.34 mm , the other two with 0.25～5.00 mm) . The modeling result s demonst rate that increase in volume f ractionof aggregate or in fineness of aggregate has the same effect , i1 e. , the curve of the nearest surface spacing dist ribution moves toward the smaller surface spacing ; the value of maximum possible nearest surface spacing where peakprobability occurs also decreases. Furthermore , the result of interval cumulative probability of the nearest surfacespacing shows that more than 57 % of the nearest surface spacing probability is smaller than 10μm. Finally , the analysis of the mean value of the nearest surface spacing reveals that the mean value of the nearest surface spacing isbetween 54.6～1.1μm if the volume f raction of aggregate varied f rom 40 % to 70 %. And when the volume fractionof aggregate is kept in the range of 50 %～70 % , the linear relationship may be built between the mean value of thenearest surface spacing and the volume f raction of aggregate. The surface area of aggregate per unit volume of mortar does have influence on the mean value of the nearest surface spacing , but the ratio between them is not constant .