：According to principles of economy，the seepage control effectiveness of canals which is studied under static and dynamic conditions and with arithmetic and geometric progression of seepage control performance to time as well as with no change seepage control performance to time is studied．The judge principles and economic models have been concluded and with the examples for calculations，the economy of seepage control effectiveness of canals has been discussed．It was avoided blindness of the seepage control of canals by necessity judgment of test．