[en] Magnetization of La(Fe_1-xCo_x)_11.4Si_1.6 (x=0-0.1) compounds was measured around their Curie temperatures. Magnetic entropy changes |ΔS| were calculated using the Maxwell thermodynamic relation. The alloy of La(Fe_0.98Co_0.02)_11.4Si_1.6 has a magnetic entropy change of 23.2 J/kg K near its Curie temperature (T_c=226 K) under a magnetic field of 7 T, which involves a magnetic-field-induced paramagnetic-to-ferromagnetic phase transition (P-F) above T_c. With increasing Co content, the magnetic entropy change decreases rapidly and no field-induced P-F magnetic phase transition takes place (for La(Fe_0.94Co_0.06)_11.4Si_1.6 compound, |ΔS|=11.6 J/kg K under 7 T field at T_c=280 K). The Wigner Seitz cell calculation and thermodynamic analysis show that the Co atoms prefer to substitute for Fe in the 96i site. The nature of the magnetic transition (P-F) near T_c could be related to the preferential substitution of the less localized Co atoms, which change the spin fluctuation behavior in La(Fe_1-xCo_x)_11.4Si_1.6 compounds