Abstarct: In present research, feasibility of removal of heavy mextals including lead and chromium from wastewater using mextal-organic frxamework (MOF) nanoadsorbent was investigated. For this purpose, firstly, MIL-100(Fe) and MIL-100(Fe)/PANI composite was efficiently synthesized by hydrothermal method. Then, structural, chemical and morphological properties of the synthesized adsorbents were specified by different experimental techniques including XRD, FTIR, SEM, EDS and adsorption isotherms of N2 at 77 K (BET). The analyses confirmed an octahedral-shaped structure for MIL-100(Fe) and indicated that PANI nanofibers were grown inside the pores and on the surfaces of MIL-100(Fe). Also, relatively high special surface values (BET) of 1843.9 and 261.29 m2•g-1 n respectively, for MIL and composite were obtained. Additionally, the adsorption behavior of lead(II) and chromium(VI) was investigated using kinetics, equilibrium and thermodynamic parameters. Equilibrium analysis exhibited that the maximum uptake capacity using MIL-100(Fe) for lead(II) was 23.46 mg g-1 baxsed on sips model and for chromium(VI) was 30.45 mg g-1 by Langmuir isotherm. While, the highest uptake capacity of composite were achieved 81.76 and 72.37 mg g-1 baxsed on sips model for lead and chromium, respectively. The sorption kinetics of lead with MIL followed the pseudo 1st order model, while for chromium(VI) followed both pseudo 1st order and pseudo 2nd order models. Whereas, the adsorption kinetics with composite followed the pseudo 2nd order model for both mextals. Thermodynamic conclusions confirmed the sorption of each two mextals by MIL was a non-spontaneous process and for nanocomposite was spontaneous. Meanwhile, dominant adsorption mechanisms baxsed on activation energy by MIL were distinguished to be chemical (ion-exchange) and physisorption for lead(II) and chromium(VI), respectively. But, the sorption mechanism of two mextals by composite was physical.