β-γ angular correlation of Tm170 is investigated taking into account the Coulomb field. Both the β-γ angular correlation and β-ray spectrum can be explained by the linear combination of the first forbidden nuclear matrix elements ---[German Symbol M](βr), [German Symbol M](βa) and [German Symbol M]m(βσ×r) in ST type interaction of the Fermi theory of β-decay, and it is concluded that the changes of the spin and parity in the successive transitions of Tm170→ Yb170→ Yb170 are 1(-)-2(+)-0(+).