A computer algorithm for the automate generation of Feynman diagrams is presented in this paper.The algorithm is transferred directly from the definition formula of Feynman diagram which makes it an extremely simple algorithm.This is different from the algorithms employed in the well known Feynman diagram generators, e.g.FeynArts and QGRAF.Those algorithms are based on the graph topology, i.e.they starts from generating all the pure topologies with no physical fields attached, then fields are inserted into the topologies.Some equivalent graphs would inevitably arise from those steps and so additional procedures of eliminating these equivalent graphs needs to be implemented, which are usually annoying.While, amazingly, in the present algorithm equivalent Feynman diagrams dont appear thoroughly.The symmetry factors and signs from fermion permutation for every diagram can also be naturally generated in this algorithm.To il-lustrate the simplicity and powerfulness of this algorithm, we also present an example C program to realize it.The C program is small, the core part taking about 150 lines of codes and the whole program taking lower than 400 lines of codes, but is powerful, being able to receive arbitraiy user defined physical models in the input.