Abstract: The evaluation model(E=E_d+E_e+E_s) of the synthetical efficiency of water conservation forest in the Qilian mountains has been built up with the theory of Marxist differential land rent, taking the retio of E to I as the efficiency index T of water reservoir forest, T=E/I where I is production invesment. The material observed at the Qilian Mountains fix-position Research Station of Forest ecosystem and the data investigated from social are regarded as the metrological valuation parameters. The economic evaluation index and the metrological system have been determined. The results show that the index of the synthetical efficiency of water conservation forest in the Qilian Mountains is 11.93, among which ecological efficiency and social efficiency are 4.51 and 6.05 times as much as the immedinate economic efficiency respectively.We have affirmed that the management policies of protection, development and synthetical utilization are right at present, and various profitable departments in HeXi should return sum over 0.5% of total income from water efficiency to forestry department as reproduction cost in order to ensure the long-term development of national economic construction.

Key words: Water conservation forest, Synthetical efficiency, Differential land rent, Economic evaluation