The distributed generations（DGs） connected to the distribution system can be divided into three categories with different interfaces， including pulse-width modulation（PWM） inverter based， the synchronous generators， and the induction generators respectively. With the raising DG penetration， it is increasingly demanding for accurate short circuit calculations. An improved short circuit current calculation method is proposed for the distribution system containing DGs. With this method，some state variables of the DGs in normal operation are obtained firstly via power flow calculations.During short circuit conditions，parts of state variables will be kept constant in terms of different DGs interface characteristics， and then short circuit current supplied by different DGs can be calculated. The presented method has been verified in a 20-bus distribution system，and the results indicate the feasibility and validity of the proposed method.