The invention discloses a method for determining heat source model parameters of single wire submerged arc welding numerical simulation. The method comprises the following steps: I, establishing a double ellipsoid heat source model to obtain a heat flux density distribution function; II, establishing a finite element model to simulate a temperature field, and taking a set of welding voltage, welding current, welding speed and welding angle which is matched with single wire submerged arc welding as a base parameter of simulation to obtain a set of appropriate double ellipsoid heat source model parameters based on experimental results; III, adjusting the double ellipsoid heat source model parameters obtained in step II by 10%, and implementing finite element numerical simulation on each parameter combination to obtain multiple sets of sample values of weld width and weld penetration so as to determine sensitivity equations of the double ellipsoid heat source model parameters and the welding speed to the weld width and weld penetration; IV, ignoring the parameters that affect the sensitivity equations slightly to obtain the simplified sensitivity equation; and V, promoting and verifying the equations. Compared with a traditional method for artificially searching the heat source model parameters, the method disclosed by the invention is high in efficiency and can be used for greatly reducing the calculating time.