The invention provides artificial marble sawdust flexible putty for external walls. According to the formula, the flexible putty is prepared from the following raw materials in parts by mass: 20-40 parts of cement, 20-70 parts of sawdust, 0.2-3 parts of a thixotropic lubricant, 0.2-0.5 part of a water-retaining agent, 0.5-6 parts of polymer micelle powder and 0.05-0.3 part of a hydrophobic agent. The flexible putty is prepared by taking organic polymer artificial marble sawdust as filler; the prepared putty is good in flexibility and crack resistance, simple in production technology and low in cost, and can adapt to certain deformation of a base layer without cracking; the artificial marble sawdust flexible putty for the external walls is suitable for leveling construction of the base layer of a plastered wall surface, a concrete wall surface, an interlocked masonry wall surface, a gypsum board, an Eterpan and the like, and is good in compatibility with fluorocarbon paint, texture paint, really stone paint and the like and better in construction effect.