The invention relates to a half-offline mixed stacking method and system as well as a robot. The method comprises the following steps of: obtaining parameter information of a tray and attribute information of boxes in a cache region, and coding all boxes in the cache region to generate an initial stacking sequence; obtaining serial number of the target box from the initial stacking sequence according to a pre-selecting rule, and stacking the target box on the tray; supplementing the boxes in the cache region, keeping number of the boxes in the cache region unchanged, updating a stacking sequence of the boxes in the supplemented cache region according to a set numbering rule to generate an updated stacking sequence and the serial number of the target box, and stacking the target box on thetray. The stacking method disclosed by the invention can solve the online mixed stacking problem of the logistics industry, can perform mixed stacking on rectangular boxes of different dimensions, canguarantee stacking stability, realizes horizontal and layered stacking, and has the advantages of being good in stacking stability, convenient for robot stacking, relatively high in tray utilizationrate and the like.