An indoor temperature control system includes a server, a first temperature sensor, a second temperature sensor, and a third temperature sensor. The server obtains a first heat adjustment amount according to a first temperature value of the first temperature sensor. The server obtains a second heat adjustment amount according to a second temperature value of the second temperature sensor. The server obtains a predetermined amount of heat of a predetermined region according to a third temperature value of the third temperature sensor. The server obtains a heat flow simulation diagram according to the first heat adjustment amount, the second heat adjustment amount, and the predetermined amount of heat. The server determines an operating time of an air conditioning device based on a target temperature, the second temperature value, and the heat flow simulation diagram.