Abstract: Free net adjustments mainly fall into three kinds: the commonly used rank-defect network adjustment, the quasi-stable adjustment and the (norm) weighted rank-defect adjustment, of which the last one is the general form. This essay argues that s (1) the results obtained from these adjustments can be transformed one another without calculating d-order inverse matrix, (2) the solutions derived from them, just like that gained from the classical free net adjustment, are unbiased. Among them x_r is the best unbiased estimation, x_s is partly best and x_p is the best with weight.