Feasibility of the measurement of the trilinear self-coupling of the Higgs boson is studied at centre of mass energy of 800 GeV. Double-Higgs strahlung as well as WW fusion processes has been investigated with a realistic simulation of a typical detector. With the combinaison of the two processes, the self Higgs coupling may be measured with a 14% precision when an integrated luminosity of 2 ab-1 would be collected at the Linear Collider.