Abstract: The inequality constrained least-squares estimation in adjustment model is studied from an entirely novel angle.Inequality constrained least-square problems are first changed to convex quadratic programming problems and then solved for the optimal solutions.The necessary and sufficient conditions on the solvability for optimization solution are given,which consequently gives the general form of least-squares estimation in adjustment model,as well as algorithm that are simple and easy to understand.A comparative calculation of a simulation example indicates that this algorithm can be applied to adjustment computation in the practical measurement.