Provided are a digital oscilloscope and a method for controlling the same. The digital oscilloscope comprises a trace intensity synthesizer including a first intensity memory and a second intensity memory. The controlling procedure performed by the digital oscilloscope includes: a determining step for determining whether the time interval of a trigger signal is larger than a predetermined threshold, a first fluorescence processing step performed when the time interval of a trigger signal is equal to or less than the predetermined threshold, and a second fluorescence processing step performed when the time interval of a trigger signal is larger than the predetermined threshold. The digital oscilloscope can automatically select the dynamic fluorescence effect to pay attention to the long-term variation of a signal when the triggering rate is low, and the static fluorescence effect to pay attention to the rapid variation of a signal when the triggering rate is high.