Abstract: The energy is the most constraint of the applications of wireless sensor network (WSN) .Reducing energy consumption is a key problem in WSN.A kind of processing problem of slow-changing data monitoring system was researched.An improved data reduction algorithm was proposed and the measurement error was considered.The data traffics were reduced by using the integrated digital filter and the above algorithm, so the lifetime of WSN was prolonged.Eventually, three spline data interpolation was adopted and the experiment results show that the temperature curve is much smoother through this method.The approach is proven feasible, practical and worthy of using abroad.