Participatory　sensing　is　the　concept　of　recruiting　mobile　devices　to　collect　data　and　engage　computing.　However,　there　are　many　problems　in　this　mode　of　cooperation,　poor　quality　of　received　information　caused　by　task　executors　has　been　one　of　them.　So　incentive　mechanism　is　proposed　for　attracting　users　to　participate　in　and　submit　high-quality　data.　Inspired　by　contract　theory,　we　model　participatory　sensing　as　a　contractual　relationship　and　design　rewards　for　multiple　results　depending　on　the　quality　requirement　of　tasks　which　maximize　the　benefit　of　task　publisher.　Under　complete　information　scenario　where　task　executors＇　efforts　can　be　observed　and　incomplete　information　scenario　where　task　executors＇　efforts　cannot　be　observed,　we　obtain　optional　contract　for　task　executors　respectively　through　solving　maximization　problem.　Finally,　we　evaluate　our　contract　based　approach　by　thorough　simulations　to　show　its　effectiveness　and　accuracy　and　analyze　the　influence　of　result,　cost　and　probability　on　reward　from　aspects　of　theory　and　reality.