On the basis of numerical calculations it is considered ultrarelativistic acceleration of electrons in space plasma by the electromagnetic wave packet propagating across the external magnetic field. The conditions for electrons capture by wave packet , the dynamics of velocity components and the particle momentum are considered in the dependence on problem incoming parameters including the wave packet size. The structure of phase plane of the accelerated electrons is considered also. The optimal conditions for the realization of ultra-relativistic surfatron acceleration of electrons by spatially localized wave packet are formulated. It is discussed the possibility of appearance of differences in the accelerated electrons from the standard power dependences.