The invention discloses a method for calculating credit for a credit system. The method comprises the following steps: a node i transmits a request to nodes surrounding a node j requiring calculating credit, and inquires the surrounding nodes about evaluation to the node j; the surrounding nodes return the evaluations; according to irrelevance of each evaluating node and reliability of the irrelevance, the node i modifies the evaluations provided by the evaluating nodes; the node i fuses actual experience of the node i and the service node j with the modified evaluations of the evaluating nodes to calculate the final credit. By applying the method, the credit system has tiny interference to a good node, and increases identifying rejection rate to a bad node, so that the calculated credit value is not affected by the bad node, thereby greatly improving the availability and reliability of the credit system.