Abstract: In this paper,a theoretical nomogram for the coda shape function was presented for type DD-1 short-period seismograph based on AM's single backscattering model,the measuring .method of the synthetic coda shape function was devised,and the average quality factor Q in the crust of Jiangsu province was estimated. The observation of coda shows that,the coda shape function is made up of two or more branchs,and the distributiqn of Q estimated by one of these branchs can correspond well with the seis-micity of the Jiangsu area.