This invention discloses an analyzing method for detecting a specific analyte in a fluid sample. The method comprises the following steps. First, a substrate is provided. The substrate has a channel provided concavely on an upper surface thereof. The channel comprises a first area, a second area and a third area, and these three areas are connected sequentially. Each of the second and the third areas comprises a nitrocellulose layers containing a reaction material and formed at the bottom thereof. The nitrocellulose layer of the third area can absorb a fixed volume of the fluid sample. Second, the fluid sample is applied to the first area and delivered by the second area and then to the third area. Finally, the reaction material reacts with the specific analyte in the fluid sample to produce a signal for detection.