In order to improve the stall margin and decrease the rotor attack angle of a highly loaded two-stage fan at off-design speed

different forms of variable inlet guide vane(VIGV) and traditional adjustable inlet guide vane were simulated

and the aerodynamic performance and internal flow field of highly loaded two-stage fan were analyzed. The numerical simulation results show that: at the 80% design speed

the highly loaded two-stage fan's adiabatic efficiency increases obviously with the increase of the VIGV's positive prewhirl

and the adiabatic efficiency increases 3.5% with prewhirl angle of 30 degrees; although traditional adjustable inlet guide vane has a better effect on the expanding stability

the loss is biggest when it needs a large prewhirl angle; the slot form

the slot position and the solidity of VIGV have a considerable influence on aerodynamic performance

with the design depending on the particular working conditions of the highly loaded two-stage fan.