This is part of joint work with Steve Kudla and Michael Rapoport. We will first describe how to write the L-function of a modular form as an doubling integral against some Eisenstein series on Sp(4), following Piateski-Shapiro and Rallis. We will then explain how to relate the central derivative of the Eisenstein series with Height pairing of Heegner divisors. Finally we put them together to obtain a variant of the Gross-Zagier formula, and also a variant of Gross's formula on central L-value.