The short-range order structures in ternary ZrF4-BaF2-ErF3 glasses have been studied by X-ray absorption fine structure (XAFS). The near-neighbor structures around Zr, Ba and Er have been determined and compared with that in binary ZrF4-BaF2 glasses. The near-neighbor structures around Zr and Ba are scarcely affected by doping with ErF3. The structural parameters of near neighbors around Er in the glasses are near to that in ErF3, but the corresponding distance and coordination number of near neighbors in the glasses decrease slightly. It is also observed that the intensities of the white lines at the Er L(parallel to) and L() absorption edges in these glasses are different from that in c-ErF3. Meanwhile, compared with that of the corresponding fluoride, the changes of the 'white line' at the Er L(parallel to,)-edges in the glasses differ from the case of Nd. The causes leading to these differences are discussed.