[Objective] To investigate the effects of microplastic types and sizes on the infiltration process of carbonatite laterite soils, and to provide new data support for further revealing the hydrological processes of microplastic-contaminated agricultural soils. [Methods] The infiltration rate, cumulative infiltration and depth of wetting front and changes with infiltration time of polyethylene PE, polypropylene PP and polystyrene PS microplastics with different particle sizes (550μm, 150μm and 50μm) were investigated by indoor flat soil column infiltration simulation tests using a fixed-head vertical infiltration method, and further evaluated with the cumulative infiltration model, Philip's model, Horton model and Kostiakov model for carbonatite laterites containing microplastics, as well as utilizing the inverse slabs of measured data in the Hydrus-1D model to derive five hydraulic parameters (θr、θs、α、n、Ks)under different microplastic treatments. [Results] ① The infiltration rate and cumulative infiltration of PS microplastics increased with decreasing particle size, while the cumulative infiltration and infiltration rate of PE and PP microplastics showed first increase and then decrease with increasing particle size, in which the difference of cumulative infiltration between different particle sizes was significant (P<0.05); in terms of the advancement of the depth of wetting fronts, PS would switch from promoting the water transport toward the deeper part of the soil to impeding the deeper water In terms of wetting front depth advancement, PS would switch from promoting water transport to deep soil to hindering deep water transport, while both PP and PE acted to promote water transport. ② In terms of model applicability, according to the evaluation indexes, all models showed good applicability, among which the Horton model and the cumulative infiltration model had the highest applicability, with R2 and CE greater than 0.98, and the average value of RRMSE was 0.10. ③ In terms of the derivation of the five hydraulic parameters, θr, θs, α, n, and Ks showed only slight differences among treatments, among which the noteworthy ones were Among them, it is noteworthy that the saturated hydraulic conductivity of PS microplastics showed a tendency to increase with the decrease of particle size. [Conclusions] The effects of PS, PP, and PE microplastics on soil infiltration processes were significantly different, and the Horton model, cumulative infiltration model, and Hydrus-1D model showed high applicability, which provided new data references for the range of hydraulic parameters in similar soil conditions.