Liquid fuel spill fires usually occur in the oil storage and transportation industries. The fire develops as the burning fuel spreads, posing a huge threat to the facilities nearby. In this paper, continuously released liquid fuel spill fires were experimentally investigated in one-dimensional channels with three different widths. The spread and burning behavior of the spill fire on water and on a horizontal steel plate were discussed in terms of the burning rate, spread rate and fuel thickness. The burning rate, estimated as the ratio of the discharge flow rate to the steady burning area, was slightly higher for the spill fire on water. The burning rate increased with the trench width, a similar tendency as that of the pool fire, but its value was much lower than that of the pool fire with the same dimensions. A method for estimating the burning fuel thickness at the flame front was proposed, and the estimated values corresponded well to the theoretical values calculated based on the balance between the gravitational force and surface tension. The spread rate of the spill fire was correlated as an exponent function of the ratio of the volumetric discharge flow rate to the trench width. The width of the one-dimensional liquid fuel spill fire mainly affected the burning rate and spread rate.