Generalizing results of our previous work (where classical kinetic energy has been used) in this work (where ultra-relativistic kinetic energy is used) we suggest an original variant of the determination of minimal length (corresponding to Plank length) by formation of a microscopic (tiny) black hole. Like to some previous authors we use Heisenberg coordinate-momentum uncertainty relation, on the one hand. But, instead of metric fluctuation (obtained by second derivative in Einstein equations) that generalizes uncertainty relation by an additional term, used by previous authors, we use Hawking temperature of the black hole and standard Heisenberg coordinate-momentum uncertainty relation.