PURPOSE: A power train of auto transmission is provided to improve lubrication and cooling of the auto transmission. CONSTITUTION: A deceleration planet gear set outputs rotation of an input shaft(10) as deceleration rotation. A complex planet gear set selectively receives deceleration rotation and non-deceleration rotation from the input shaft and the deceleration planet gear set, and outputs multi stage transmission rotation to an output shaft(20). The deceleration planet gear set comprises first to third operation elements. The complex planet gear set comprises fourth to seventh operation elements. The seventh operation element is selectively constrained to a transmission case(30) as being selectively connected to the input shaft.
