In this work, the flocculation behavior of suspension systems containing poly(acrylic acid) (PAA) with different molecular weights and aluminum oxide particles was studied fundamentally. Correlations were developed among the adsorption of PAM on the particles, the zeta potential of the aluminum oxide suspensions and the turbidity of the suspensions. The structure of flocs formed between PAA and aluminium oxide particles were comprehensively studied under stirring and non-stirring conditions. The fractal dimension, D-f, of the flocs ranged between 1.1 and 2.4 revealing that the flocs generated by PAAs could be considered as fractals. The flocs formed by PAA with molecular weights of 100 kg/mol (PAA-100k) and 450 kg/mol (PAA-450k) were more compact (D-f of 1.418), while those formed by PAA with the molecular weight of 1250 kg/mol (PAA-1250k) were larger and random-shaped with loose and porous structure (D-f of 1.179). The presence of 3 mg/g of PAA-1250k in aluminum oxide suspension increased the chord length of particles dramatically. Reasonable relationship was developed between settling velocity and chord length of flocs, and flocs with smaller fractal dimension and sediment compactness had faster sediment kinetics.