Abstract: Considering the profitability, risk sustainability and creditability of credit guarantee institution, a DEA-based efficiency evaluation was made to the composite operational efficiency including technical efficiency and scale efficiency of credit guarantee in a province of Northeast China with an empirical analysis made to the input redundancy and output deficiency. The results showed that most of the credit guarantees are in an inefficient state where although the technical efficiency is higher than the composite efficiency, it is purely not technical in fact. At present the credit guarantee is highly competent to take advantage managing techniques to decrease the input with the output level raised simultaneously, but most of credit guarantees are in a diseconomic scale state with both input redundancy and output deficiency. The fact implies that the credit guarantee cannot make its due contribution until the subsequent input is reasonable with corresponding output.