The invention discloses a plug 
seedling substrate of tomatoes and a preparation method. 
Peat is taken as the material; excrements of livestocks are taken as 
earthworm foodstuff; environment suitable for the growth of earthworms is provided; wormcast which is processed and generated by the earthworms is sieved to obtain wormcast 
compost with the grain size being 1-4mm; and the 
peat and the wormcast 
compost are fully mixed; mineral materials with a certain 
fineness such as expandable 
vermiculite, 
perlite and the like are added to improve the physical properties and the buffer performance of the substrate to generate a novel tomato 
seedling substrate. The percent by volume of various components are that the 
peat accounts for 15-25%, the wormcast 
compost accounts for 55-65%, the expandable gardening 
vermiculite accounts for 5-15% and the 
perlite accounts for 5-15%. The plug 
seedling substrate disclosed by the invention has the advantages of simplicity in preparation method, richness in resource, low cost of materials, turning waste into wealth, reducing environmental 
pollution and sufficient 
nutrient. The plug seedling substrate is used for the plug seedling of tomatoes, eliminates top application during seedling raising, improves the quality of tomato seedlings and reduces the 
pesticide application. Thus, the seedling quality is ensured, the cost and the labor are saved and the survival and the high-quality and efficient growth of the tomato seedlings, the yield and the construction of quality are ensured.