As　one　of　the　key　components　in　the　non-volatile　full　adder　(NV-FA),　spin　transfer　torque　assisted　voltagecontrolled　magnetic　anisotropy　magnetic　tunnel　junction　(STT　assisted　VCMA-MTJ)　will　possess　superiordevelopment　prospects　in　internet　of　things,　artificial　intelligence　and　other　fields　due　to　its　fast　switchingspeed,　low　power　consumption　and　good　stability.　However,　with　the　downscaling　of　magnetic　tunnel　junction(MTJ)　and　the　improvement　of　chip　integration,　the　effects　of　process　deviation　on　the　performances　of　MTJdevice　as　well　as　NV-FA　circuit　become　more　and　more　important.　Based　on　the　magnetization　dynamics　ofSTT　assisted　VCMA-MTJ,　a　new　electrical　model　of　STT　assisted　VCMA-MTJ,　in　which　the　effects　of　the　filmgrowth　variation　and　the　etching　variation　are　taken　into　account,　is　established　to　study　the　effects　of　theabove　deviations　on　the　performances　of　MTJ　device　and　NV-FA　circuit.　It　is　shown　that　the　MTJ　state　fails　tobe　switched　under　the　free　layer　thickness　deviation　gtf　＞=　6%　or　the　oxide　layer　thickness　deviation　gtox　＞=　0.7%.　The　sensing　margin　(SM)　is　reduced　by　17.5%　as　the　tunnel　magnetoresistance　ratio　deviation　b　increasesto　30%.　The　writing　error　rate　can　be　effectively　reduced　by　increasing　Vb1,　and　increasing　Vb2　when　writing　＇0＇or　reducing　Vb2　when　writing　＇1＇　in　the　NV-FA　circuit.　The　output　error　rate　can　also　be　effectively　reduced　byincreasing　the　driving　voltage　of　logical　operation　Vdd