In this paper, using the variometer data of Changli station and Baijiatuan station from 1972 to 1997, the inter-station transfer functions of horizontal field and the single-station transfer functions of vertical field have been calculated. With analyzing the whole changing process of the transfer functions, we have discovered that only the horizontal field transfer functions arose obvious short-term precursors before Tangshan earthquake. This fact may provide a new method for short-term prediction of earthquake. In this paper, using the variometer data of Changli station and Baijiatuan station from 1972 to 1997, the inter-station transfer functions of horizontal field and the single-station transfer functions of vertical field have been calculated. With analyzing the whole changing process of the transfer functions, we have discovered that only the horizontal field transfer functions arose obvious short-term precursors before Tangshan earthquake. This fact may provide a new method for short-term prediction of earthquake.