In this paper,first,a Dirichlet series expression of concrete creep based on the generalized Kelvin mod-el with variable coefficients is suggested,and a creep expression with nine parameters is proposed based on the con-tinuous retardation spectrum.Then,an expression of relaxation coefficient rate is derived and a rate- type superposi-tion algorithm is further proposed to calculate the relaxation coefficient.Finally,by using some experimental data,the suggested creep expression and the rate- type superposition algorithm are respectively compared with the commonones.The results indicate that (1) the proposed creep expression possesses explicit physical meaning and helps toavoid negative creep; (2) the creep expression with nine parameters is of higher fitting precision,as compared withthe expression with eight parameters; and (3) the proposed rate- type superposition algorithm helps to avoid the er-ror propagation existing in the traditional superposition algorithm and greatly improves the fitting precision of theearly- age concrete at longer lag- time stage.