Effects of process variables and material properties on melt spinning of pitches have been studied based on simulation using governing equations by Kase and Matsuo. It is shown that the tensionFin a filament depends on spinning conditions as well as viscosity of pitch in the form ofF∝μ0W1/6f1(v0,vL,vA)/f2(T0,TS,TA,E). Here,W,v0,vL, andvAare mass flow rate, velocity at the spinnerette, winding speed and cross‐flow air velocity respectively, andT0,TS, andTAdenote temperatures at the spinnerette, at the solidification point and of air. Temperature dependence of viscosity is simplified by an Arrhenius type equation with a pre‐exponential factor μ0and a flow activation energyE. To improve spinnability, the maximum tensile stress σLshould be decreased by increasingW,T0andTAor by decreasingvL,vA,TS, μ0andE. In other words, slower cooling of the filament with larger diameter for a pitch with smaller activation energy is preferable to better spinnability. Effects of these factors on diameter, temperature and strain rate of the spinning filament are also discussed.