A method for identification of source terms for inverse heat conduction problems in steady state  was presented. Based on finite element numerical solution, an explicit formula for numerical general solution was constructed, which satisfied the heat conduction governing equations and boundary condition, taking the intensity of heat source as the variable with discrete form. The method converted the heat conduction inverse problem to multivariables limit problem, which made the identification of intensity of heat source easy. The basic computational formula was derived, the mathematics modeling problem of identification of intensity of heat source for inverse heat conduction problems was discussed and  error analysis was conducted. Taking the heat source design of mould heating plate as an example, the correctness and practicability of the algorithm was validated, which is of importance for further investigation of identification of space of heat source and multidimensional source terms for inverse heat conduction problems.