We have proposed the sensorless model control based on the static model equation of the dc-dc converter that is able to change the bias value corresponding to changes of the load current, the input voltage and output voltage. The sensorless model control can regulate the output voltage. On the other hand, the transient response of output voltage is not improved. Therefore, an improvement of the transient response is carried out by adding the transient improvement function which changes a bias value drastically for a short time at the start of the transient state. The purpose of this paper is to indicate the parameter setting of the transient improvement function that improves the transient response by the simulation analysis under changing the circuit condition.