Abstract: A SDT(Swinging Door Trending)algorithm with low computation cost is generally used in process data compression. The modified SDT algorithms, include offline and online compression and information retrieve, are presented to enhance compression performance. Simulation results demonstrate that the algorithm is better than the original one in the performance index of maximum error and sum of squared error. The Neuron C program is written and downloaded into the self designed data acquisition nodes, online use of the modified algorithm is therefore implemented.