Aiming at estimating parameter and model stability in the discrete GM(1,1), this paper discusses three methods: the least square method,the least absolute deviation and accumulating method. In order to compare the differences of different estimation methods, the same initial values are uniformly assigned. Taking fitting error, degree of relevance and conditional number as evaluating indicators, the paper uses the MATLAB software to analyze two kinds of instance data: increasing sequence and decreasing sequence. The results show that the accumulative method is better than the least absolute deviation and least square method in the aspect of error, and accumulation method is superior to least square method in the aspect of stability. In summary, the cumulative method is best to estimate parameters in GM (1,1).