Abstract：In order to study the influence of system error on parameter estimation through theory analysis,the parameter estimation unbiasedness,the effectiveness,and the unbiased estimate of unit weight variance are studied. The results show that:( 1) parameter estimation is unbiased whether an adjustment model exists system error;( 2) unit weight mean error estimation unbiasedness has no relationship with system error;( 3) the parameter estimation precision will be reduced if the system error model is utilized under condition that systematic error does not exist;( 4) the estimation accuracy will be artificially increased if a general adjustment model is used but there are systematic errors. Therefore,the research of system error is necessary to improve the adjustment model,and the adjustment should consider the influence of system error.

Keyword：system error;parameter estimation;unbiasedness;effectiveness;unit weigh variance;