Abstract: The model of adiabatic spherical to columnar hydrogen bubble growth in large leak sodium water reaction as well as the model of secondary loop pressure propagation with the one dimensional characteristic method are established under one double ended guillotine tube break in the steam generator of liquid metal cooled fast breeder reactor. Both of the characters of large leak sodium water reaction and secondary loop pressure propagation transient are calculated and analyzed at the two phase water large leak with and without rupture disks.