Abstract: Crystals of two complex compounds of rareearth perchlorate with Lproline,[RE2(LPro)6(H2O)4](ClO4)6(RE=Pr,Er),were synthesized.Their structures were characterized using TG,DTA,chemical analytic method and comparing with literatures,and the purity is determined as 99.24％ and 98.20％,respectively.For the calculation of chemical reaction heat,solution heat of the [2RE(NO3)3•6H2O＋6LPro＋6NaClO4•H2O] and the {[RE2(LPro)6(H2O)4](ClO4)6＋6NaNO3} were firstly measured in 2 mol•L1 HCl solvent with an isoperibel reaction calorimeter,respectively.The standard enthalpy of formation of the two crystals were calculated by chemical reaction heat and a designed thermochemical cycle at 298.15 K.The following reaction enthalpy and standard enthalpy of formation were obtained: 　　RE=Pr:ΔrHm=－63.904 kJ•mol－1;RE=Er:ΔrHm=－ 91.017 kJ•mol－1; 　　ΔfHm([Pr2(LPro)6(H2O)4](ClO4)6,s,298.15 K)=－6 594.78 kJ•mol－1; 　　ΔfHm([Er2(LPro)6(H2O)4](ClO4)6,s,298.15 K)=－6 532.87 kJ•mol－1.

Key words: Perchlorate, L-Proline, [RE₂(L-Pro)₆(H₂O)₄](ClO₄)₆(RE=Pr,Er)