After inversing the x-ray surface brightness of the cooling flow cluster Abell 1689 through the isothermal β model,the isothermal double β model and the x-ray surface brightness distribution model derived from the universal dark matter density profile,we calculate the electron distribution and the Sunyaev-Zel'dovich(SZ)effect of the cluster.The resulting temperature decrements,which are inversely proportional to the square root of H0,are very different for the three models,with uncertainty of 15%.Thus,the SZ/x-ray route can not be taken as a precise measurement of H0 until further observations(e.g.from the satellite AXAF)constrain well the amount and distribution of cluster gas.
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