Eco-friendly alternative way for waste straw management is needed. Black soldier fly (Hermetia illucens) larvae (BSFL) are outstanding insects for bioconversion of organic waste, which can convert separate or mixed waste, i.e. manure, kitchen waste and straw, into biomass rich in protein and fat. In this study, through orthogonal experiment, maize straw, fermented with Aspergillus oryzae for 24 h in a ratio of 4000:1, was identified for BSFL bioconversion. Bioconversion performance of BSFL on fermented maize straw was assessed. With this fermented maize straw as feedstuff, larval stage of BSF was significantly prolonged compared with the control feedstuff (wheat bran). Adult duration was significantly shortened and the fecundity of females was significantly decreased. The harvested dry BSF larvae contained 41.76% crude protein, 30.55%, crude fibre, and 8.24% crude ash. The grease of BSFL, compared to the larvae collected from the control diet, had a higher proportion of monounsaturated fatty acid (24.86%) and polyunsaturated fatty acid (25.37%), while a lower proportion of saturated fatty acid (45.41%). Dry matter reduction of maize straw was 48.41%. After bioconversion by BSFL, the residual maize straw was significantly changed in crude protein, crude fat and nitrogen free extract content. By comparing with organic fertilizer NY525-2012, maize straw residue had a potential application in agriculture and nursery as a novel fertilizer. This new alternative method will benefit the comprehensive bioconversion of maize straw with pretreatment by insect.