Abstract: According to the effects of gross error on posterior variance, on the basis of the er-ror theory and reliability theory, the multidimensional gross errors are located and evaluated with the method of maximum variance ratio and the minimum sum of the squares of random error. Through a large number of random simulation calculations, the threshold, which jud-ges the end conditions of the search, can be obtained. After gross errors are searched and lo-cated, an estimating model is given under the conditions of the minimum sum of the squares of random error. The estimating model is tight and not approximate. After many experi-ments, the result showes that using the method not only can detect the big gross error can also detect small gross error.