Averaging of the planetary three-body problem equations in the heliocentric reference frame is realised. The complex Poincar´e canonical elements are used. The disturbing function is expanded by means of Laplace coefficients. We use the Hori—Deprit method to perform an average equations of motion at order two in the planet masses. The results of the present work can be easily generalised to the case of the general planetary N-body problem.