•TD-DCS brain detection is severely affected by present optoelectronic devices.•CW-DCS is currently still superior to TD-DCS in brain functional detection at 830 nm.•With advance of optoelectronics, TD-DCS detection ability can be enhanced. Diffuse correlation spectroscopy (DCS) is an optical technique originally used for measuring dynamic properties of multiple scattering media. Depending on the type of light source used in the system, DCS can be classified as continuous wave DCS (CW-DCS) or time-domain DCS (TD-DCS). With pathlength-resolved measurement, TD-DCS can theoretically achieve a higher sensitivity detection than CW-DCS on dynamics in deep tissue. However, TD-DCS is affected by more factors than CW-DCS such as the instrument response function (IRF), finite coherence length of the light source (Lc), photon detection efficiency (Q), thus the detection ability in the application of measuring cerebral blood flow (CBF) may be degraded. To elucidate this, we used a simulation approach with a realistic head model to show the detection ability of the two DCS techniques on measuring the functional change in CBF with the same incident light wavelength (830 nm), incident light power (75 mW) and single mode detection fiber. The result reveals that TD-DCS is less sensitive than CW-DCS in detecting human brain function in the condition of available optoelectronic devices at 830 nm. This simulation work may also provide a solution to improve the detection ability of TD-DCS on human brain.