The invention relates to a production method of a lost foam mold, in particular to a manufacturing method of a large-sized cast steel part lost foam mold. The method sequentially comprises the following steps: determining a manufacturing material of the lost foam mold; manufacturing the lost foam mold; performing surface treatment; shaping; controlling dimension in the process. According to the manufacturing method, the production cost is reduced, the manufacturing period is shortened, the production efficiency is improved, and multiple times of shaping production can be realized through one set of lost foam mold.