3 D simulation is an effective method to analyse the temperature and flow fields for separated oil-immersedcooling transformer. In this paper

the temperature and flow fields of a separated oil-immersed cooling transformer arecalculated by the finite element method

the influences of the horizontal distance between transformer and radiator ondistributions of the temperature and flow fields are analyzed

and the coupling relationship between temperature fieldand flow field is discussed. Simulation results show that:（1） the location of the hot spot is at the 0.68 height of the low-voltage winding and its temperature is 369.7 K:（2） as the horizontal distance between oil tank and radiator increases

the temperature of the hot spot rises by 3.9 K/m

and the oil temperature at the top rises by average 5.1 K/m;（3） theerrors between the calculation results and the experimental data are all less than 2.5 K;（4） the varying trend of tem-perature and flow velocity are contrary

and the maximum temperature variation will be 9.2 K as the flow velocitychanges by-4.9×10-3 m/s;and（5） as the horizontal distance between oil tank and radiator increases from 5.2 m to6.4 m

the oil flow velocity in the connecting tube between oil tank and radiator decreases from 0.067 m/s to 0.056 m/s.