The invention provides a multi-gear automatic transmission which comprises a first shaft system WS1, a second shaft system WS2, a first fixed shaft gear set TG69, a second fixed shaft gear set TG56, a third fixed shaft gear set TG17, a first planetary gear set PG1, a second planetary gear set PG2, a third planetary gear set PG3 and six gear shift elements including a first brake B1, a second brake B2, a first clutch C1, a second clutch C2, a third clutch C3 and a fourth clutch C4; power is input through the first shaft system WS1, output to a differential mechanism Diff. through the second shaft system and then transmitted to wheels on the two sides through outputs at the output ends of the two sides of the differential mechanism. The first shaft system is parallel to the second shaft system, and the multi-gear automatic transmission is particularly applicable to a preposition front-drive type vehicle; the structure is compact, vehicle gearshift response can be faster, the dynamic property is higher, and the vehicle can have better driving performance and better fuel economy.