A fluid quality tracing method includes obtaining pieces of fluid concentration distribution data of a detected region corresponding to detection time points respectively, generating pieces of concentration grid data respectively according to the pieces of fluid concentration distribution data, obtaining pieces of fluid moving data of the detected region corresponding to the detection time points respectively, obtaining estimated positions according to the fluid moving data and an initial position, and creating a fluid concentration trajectory according to the pieces of concentration grid data, the initial position and the estimated positions. The initial position and the estimated positions are located in the detected region. The fluid concentration trajectory includes line segments with terminals corresponding to the initial position and the estimated positions respectively, and the line segments indicate concentration representative values respectively.