119Sn M(o)ssbauer research is carried out on (La1-xSrx)2Cu1-xSnxO4 (x=0.075 and 0.110) superconductors which are designed under a new concept. The M(o)ssbauer spectra results show that Sn occupies Cu position in Sn4+ state, and there is no Sn2+ ion occupying La position. The local lattice deformation near Sn4+ site is small, but displays an increasing tendency with Sn doping. For La2CuO4 matrix, the simultaneous dopings of Sr/Sn induce holes and electrons on CuO2 layer in a new mechanism which influences superconductivity. Under a new mechanism of extra oxygen, the extra oxygen effect of Sn-doping on superconductivity is discussed.