The invention discloses an electric vehicle start control method and system. According to the method and system, condition monitoring is conducted on a main relay firstly before precharge during starting of an electric vehicle, so that the situation that a precharge resistor is damaged by large currents generated when a precharge subcircuit is closed under the condition that the main relay is in the normally closed breakdown state is avoided; furthermore, the charging time of a capacitor is monitored during precharging, whether the charging time is within a preset time range is judged, and the main relay is closed to start the electric vehicle only when the charging time of the capacitor is within the preset time range, so that the situation that the capacitor is charged for a long time through the precharge subcircuit due to circuit opening, short-circuit fault or misoperation of a driver is avoided and damage of the precharge subcircuit due to long-time current passing is avoided.