The Proterozoic Mayuan group is well developed in Northern Fujian province. 7 samples of epi-meso metamorphic rocks from the Mayuan gronp and 2 samples of muscovite granites were taken to be measured by Sm-Nd and Iib-Sr radioactive isotopic method, The Sm-Nd isotopic isochron age of whole rock for 7 samples is 2116±22(2σ)Ma, INd=0.51027+2(2σ)，εNd (t)=7.29+0.17. Ab-Sr isotopic isochron age of whole rock for 6 samples is 375+28(2σ)Ma, 87Sr/86Sr(i)= 0.703+3(2σ); The age of 2116Ma, the earliest age of strata in Fujian and Jiangxi provinces, represents a formation age of the Mayuan group and the age of 375Ma 一一metamorphic age of the Mayuan group. From the data of εNd (t) and 87Sr/86Sr (i), it may be postulated that original rocks of the Mayuan group in Northern Fujian province had been mostly formed through volcanism.