The invention relates to an assembling mould of a B7 contact ball bearing, which comprises a round assembling mould terrace, and is characterized in that the terrace is provided with a taper table figure central positioning table; a steel ball positioning table for positioning a bearing steel ball in the process of assembling is arranged at the housing washer of the central positioning table; the steel ball positioning table is a stepped table, and the step is a two-grade step higher inside and lower outside. The method for assembling the B7 contact ball bearing includes the following steps: the retainer is sheathed on the assembling mould along the axial direction; the heated housing washer is sheathed on the retainer along the axial direction; the steel ball slides along the top taper part of the assembling mould to be located in a jolt; an inner race is inserted along the axial direction. The assembling mould has the following advantage: as each spare part can be precisely located by being assembled on the positioning mould, and lipid is not needed for adhesion, and the assembling time is shortened, the whole process is guaranteed to be completed in the range of an allowed retraction for the cooling of the housing washer, so that the assembling mould of a B7 contact ball bearing has the effect of fast and accurate assembling.