A stellar chromospheric activity spectral database of solar-type stars is constructed based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low-Resolution Spectroscopic Survey (LRS). The database contains 1,330,654 high-quality LRS spectra of solar-type stars with effective temperature ranging from 4800 K to 6800 K. We measure the mean fluxes at line cores of the Ca II H&K lines using a 1 Å rectangular bandpass as well as a 1.09 Å full width at half maximum (FWHM) triangular bandpass, and the mean fluxes of two 20 Å pseudo-continuum bands on the two sides of the lines. Three chromospheric activity indexes, Srec based on the 1 Å rectangular bandpass, and Stri and SMWL based on the 1.09 Å FWHM triangular bandpass, are evaluated from the measured fluxes. The uncertainties of all the obtained parameters are estimated. We also produce spectrum diagrams of Ca II H&K lines for all the spectra in the database. This database with more than one million high-quality LAMOST LRS spectra and basal chromospheric activity parameters can be further used for investigating activity characteristics of solar-type stars and solar-stellar connection. The entity of the database is composed of (1) a catalog of spectral sample and activity parameters, and (2) a library of spectrum diagrams. (1) Catalog of Spectral Sample and Activity Parameters CaIIHK_Sindex_LAMOST_DR7_LRS.csv (2) Library of Spectrum Diagrams spectrum_diagrams_000-049.zip (46 subfolders) spectrum_diagrams_050-099.zip (40 subfolders) spectrum_diagrams_100-149.zip (47 subfolders) spectrum_diagrams_150-199.zip (49 subfolders) spectrum_diagrams_200-249.zip (47 subfolders) spectrum_diagrams_250-299.zip (45 subfolders) spectrum_diagrams_300-349.zip (41 subfolders) spectrum_diagrams_350-399.zip (39 subfolders) spectrum_diagrams_400-449.zip (45 subfolders) spectrum_diagrams_450-499.zip (35 subfolders) spectrum_diagrams_500-549.zip (27 subfolders) spectrum_diagrams_550-599.zip (38 subfolders) spectrum_diagrams_600-649.zip (32 subfolders) spectrum_diagrams_650-699.zip (26 subfolders) spectrum_diagrams_700-749.zip (28 subfolders)