The invention discloses a control method for display fields of an instrument. The control method is executed by an instrument device cooperating with multiple monitoring devices which can be on-line with the instrument device. The instrument device comprises a screen, a memory and a processor. The method comprises the following steps: (A) the memory pre-stores multiple pieces of field configuration data, and the processor displays measured values measured by a first group of monitoring devices on the screen according to one piece of field configuration data; (B) the processor detects an on-line state, judges whether the instrument device is on-line with the first group of monitoring devices or not, and if no, enters step (C); (C) the number of the on-line monitoring devices is calculated; (D) the processor reads a piece of field configuration data corresponding to the number of the on-line monitoring devices from the memory, and correspondingly displays the measured values measured by the on-line monitoring devices on the screen. According to the control method, a field configuration manner is automatically regulated by detecting the on-line state, and information is displayed in a more striking manner.