Abstract: The disclosure provides a parallel inversion method and system for a ground-based transient electromagnetic (TEM) method. The method includes acquiring observed TEM response data; dividing an inversion domain into unstructured tetrahedral grids and set a conductivity value, and constructing an initial inversion model and a regularized objective function; calculating the product of the sensitivity matrix and vector of the model parameters; converting the objective function into a least-squares problem by using the Gauss-Newton method, obtaining the model update direction, and using line search to obtain the optimal model update step length to update the inversion model; performing 3D TEM forward modeling based on the vector finite element method, and obtaining the predicted TEM response data; using the normalized error to evaluate the fit between the predicted TEM response data and the observed TEM response data; if the normalized fit difference reaches a preset threshold, the inversion method is terminated.