Abstract: The differential formula between the 3-D baseline vector(ΔX ΔY ΔZ)^T and its corresponding geodetic coordinate difference(ΔB ΔL ΔH)^T has been derived in this paper.Its application to transformation of baseline vectors between coordinate systems,to studying of differential structure of some geodetic quantities,to studying of error propagation and to transformation of the covariance matrix of GPS baseline vector to the covariance matrix referring to the geodetic reference system or Gauss-Kruge plane coordinate system has also been discussed.