We investigate the high-resolution thermoelectric power of Bechgaard salt (TMTSF)2ClO4 in temperatures between 6 and 280K for metallic state with different cooling rates through the anion-ordering transition Ta=24K. There is a linear temperature-dependent thermoelectric power at high temperatures, which cannot be explained by conventional one-dimensional(1D) electron band theory. A sudden change of the slope at about 240K is observed for the first time. Below 140K, the curve deviates from linear behavior and goes down all the way through, which is attributed to a 1D—2D crossover. Comparing with the results of specific heat and resistivity with different cooling rates through the anion-ordering transition at 24K, no clear trace of anion-ordering transition can be spotted in thermoelectric power by the slowest cooling process unless we take differentiation of the data and we found a gradual rise in thermoelectric power with increasing cooling rate through the Ta for the first time. The influence of anion-ordering transition is discussed.