Abstract: In the 3D coordinate transformation,change of two datum system origins ΔX,ΔY,ΔZ,scale change factor λ and three rotate angle θ,,ψ are generally used as parameters,a total of seven changes is called seven-parameter transformation.There are three transformation models,the Buras-Wolf model and the Molodensky model and the WTUSM model,generally used between two datum systems transformation.The linear models is used when the rotate angles are small;however,when the rotate angles are bigger,model errors will be produced relatively.