We investigate magnetic properties and electronic structure of graphene-based nano-spin valve-like structures by using nickel layers as ferromagnetic layers grown on both sides of graphene theoretically. Three different stacking arrangements of nickel and graphene layer based on basic adsorption of graphene on the top of Ni(111) are considered to understand the stablest stacking arrangement of nickel layer on both sides of graphene [1]. We model our system by using a density functional theory (DFT)-spin GGA based simulation [2]. Two magnetic alignment condition, antiferromagnetic (AFM) or antiparallel configuration and ferromagnetic (FM) or parallel configuration, for upper and lower nickel slabs was used in the simulation. Total energy calculation shows AFM configuration has the lowest energy state in the stablest stacking arrangement which is in agreement with previous experimental studies [3] and the total energy difference between AFM and FM configuration is in the order of meV which implies the magnetic configuration change does not need high external magnetic field. The spin-charge density mapping and bandstructure results show the preferable AFM configuration state comes mainly from magnetic interaction between the nickel layer and graphene and magnetic configuration of carbon atoms within graphene. The preferable AFM configuration state also consistent for various thickness of nickel layer. Band structures of Ni/graphene/Ni nanostructure also show the dependence of in-plane conductance of graphene layer to the magnetic alignment of two nickel slabs; a band gap at the Dirac cone is open when the alignment is AFM configuration and it is close when the alignment is FM configuration. Both magnetic properties and electronic structures of Ni/graphene/Ni nanostructure lead it to become a prospective spintronic device of in-plane magnetoresistance for graphene-based nano-spin valve-like structures.