Influence laws of failure shape, stress strain curve, peak stress and secant modulus affected by size and spatial location of aggregate in concrete were studied under same condition based on particle flow concrete. Through analyzing the results of uniaxial compression simulation experiment of the concrete with different mortar and aggregate mass ratios(5∶5,4∶6,3∶7,2∶8) and different gradations(gradation 1, gradation 2, gradation 3 and gradation 4), it is found that aggregate has the effect of preventing crack propagation, the larger the aggregate, the greater the effect of preventing crack propagation, micro cracks was found to occur at around the aggregate and propagate. It is proved in many micro tests, that adding aggregate in mortar can greatly improve concrete strength and deformation characteristics. Comparing to peak stress 52MPa and secant modulus 307GPa of mortar, the peak stress of different gradations with 5∶5 and 4∶6 of mass ratio increases by 22%48% and secant modulus inereses by -8%99% with average value being 65MPa and 72MPa, 374GPa and 426GPa, the peak stress of different gradations with 3∶7 and 2∶8 of mass ratio sharply increases by 40%228% and secant modulus dramatically decreases by 79%92% with average value being 92MPa and 154MPa, 158GPa and 44GPa, which proves that under the same mass ratio, the higher the aggregate gradations, the easier it is to form structure built on stilts, causing local instability and affecting the enhancement effect; under the same grading, the strength of concrete increases with the increase of the mass ratio, and the stress strain curve firstly changes from unimodal to bimodal and then back to unimodal, which suggests that the stability of aggregate spatial structure determines change of stress strain curve.