The purpose of this research is to study the diversity of cultivated crops and weeds in an Organics, GAP and Chemical crop production system of vegetable farms in Nakhon Pathom Province during January to December 2018. The results showed that the cultivated plants were found in organics, GAP and Chemical crop production systems were 19 species 15 families, 6 species 6 families and 7 species 5 families, respectively. Weeds were classified according to botanical characteristics including broad leaf weeds and narrow-leaf weeds. The organic plant production system found 13 species of broadleaf weeds and 5 species of narrow leaf weeds. GAP crop production system found 4 species of broad leaf weed and 1 species of narrow leaf weed. Chemical crop production system found 2 species of broad leaf weed and the narrow leaf weed was not found in the field. GAP and Chemical crop production systems found species of weeds less than in organic crop production. Due to the use of the herbicide (Diuron®) therefore able to get rid of most weeds.