Abstract: The estimates of variance components of Helmert type for both condition and parameter adjastmeat methods have been given in many geodetic literatures and corresponding simplified fofmulas have been respectively derived under some assumptions(e.g. the simplified formulas from Förstner,Ebner,Helmert,and Welsch,etc.) but the estimation formula of variance-covariance compnents of Helmert type is only given for the parameter adjustment.Based on a general functional model 1,a general formula of Helmert type for estimating variance-covariance components which is applicable to all adjustment methods has been derived in this paper,and directly from it a general formula and corresponding simplified formula for estimating variance components are also given.