An optical parameter measurement device and a corresponding method are provided. A light beam from a to-be-tested display panel is split by a beam-splitting assembly into at least two testing light beams. A voltage value corresponding to a first testing light beam is measured by a trans-impedance amplification circuit corresponding to a first optical sensor. Next, an integration time period is determined by a control circuit according to voltage values from the trans-impedance amplification circuit and a predetermined relational model between voltage values corresponding to the light intensities and integration time periods. A voltage value corresponding to a second testing light beam is finely measured by the integration circuit corresponding to a second optical sensor within the integration time period. Finally, the display brightness value of the to-be-tested display panel is determined by the control circuit according to a voltage value from the integration circuit within the integration time period.