Three kinds of fog seal treatments including Rejuvaseal, CAP and HAP, as well as two kinds of overlay treatments including Micro-surfacing and Novachip had been taken on a highway in Guangdong province. According to FWD investigation in 2004 years and 2006 years, t-test, rank sum test, analysis of variance and multiple comparison method are used to analysis the decay of deflection. The results show that, for delaying the strength decay of road structure, the three fog seal treatments and Micro-surfacing have significantly effect, but Novachip is poor; and the effect of Rejuvaseal is weaker than CAP, HAP and Micro-surfacing, and there is no obvious difference among the last three treatments; and the above-mentioned data analytical methods are suitable for evaluating the effect of preventive maintenance treatments.