Abstract：Based on the relation between relativity mass and speed of free microscopic particles, the relativity energy expressions of free microscopic particles and free photons were given respectively. The still mass, speed and relativity energy expressions of free neutrinos were given based on the definition of free neutrinos, the laws of momentum conservation and energy conservation. The results show that the energy of a free photon is the sum of the energy of two mutual coupling free neutrinos, that is E(c)=2E(v_n). The speed and still mass of a free neutrino are v_n=c,m_n0=m₀/2.

Keywords: microscopic particle; free neutrino; free photon；relativity；energy