Method of switching dual subscriber identity modules (SIMs) of an electronic device includes predetermining a number of sequences. Each of the sequences represents a combination of a number NUM1 of a first state value, and a number NUM2 of a second state value. The first state value represents that the SIM is available, and the second state value represents that the SIM is unavailable. When a connected base station transfers a phone call to the SIM of the electronic device and the connected base station is not the default base station, a probability of missing the phone call of the SIM with each of the sequences is calculated. Based on the calculated probabilities, an optimized sequence is determined. The optimized sequence has a minimum probability and corresponds to a maximum ratio of NUM2 to NUM1. According to the optimized sequence, a standby time of the electronic device is divided.