AbstractTo blaze new trails for utilizing forestry processing residue, higher plant content biocomposites were proposed based on a combination of moso bamboo flour/silane KH550/high density polyethylene (HDPE), and the materials were characterized by diffractometry, spectroscopy, microscopy, and calorimetry. During surface modification, reactions between bamboo and silane occurred on the lignin aldehyde group. After 6 wt% KH550 treatment, crystallinity of bamboo was increased by 1.11 %, and melting temperature and enthalpy of the composite rose by 2.37 °C and 5.27 J/g, agreeing with improved interface morphology. Increasing in thickness from 3 to 9 mm, the physical and mechanical properties of composite were improved overall. Bamboo content caused the biggest influence, while thickness swelling exhibited the greatest susceptibility. Increasing the bamboo ratio boosted flexural and tensile properties, but it compromised toughness and water resistance, while silane and moulding parameters featured complicated relationships regarding performances. Combining an artificial neural network (ANN), KH550 3 wt%, moulding temperature of 180 °C, and a time of 8 min endowed 9 mm composites of 70 wt% bamboo with performance comparable to load bearing MDF in GB/T 11718. This research helped establish the first “Bamboo Plastic Composite” standard proposed by the authors for the Chinese forestry industry.