Abstract: The aim was to clarify the weed species, community composition and damage status in paddy field of Qiqihar City, and provide a basis for effective prevention and treatment of weeds in paddy field. Using inversion "W" shape 9 sampling method, field survey and fixed point observation were carried out. The field survey included fixed point counting method and random visual observation method for the weed species, community composition and the status of damage. The results showed that the occurrence frequencies of Cyperus difformis L., Phragmites communis Trin, Echinochloa crus-galli P. Beauv., Eleocharis intersita Zinserl. etc. were decreasing, while that of Sagittaria sagittifolia L., Monochoria korsakowii Regel & Maack, Monochoria vaginalis, Alisma orientale Juzep, Leersia heraudra Swartz, Agrostis palustris were increasing in the 20 years. The extent of the damage of weeds varied with the frequency of their occurrence, and caused serious harm. Weed community in paddy field changed from“gramineous weed cyperaceous weed broad leaf weed” to“broad leaf weed gramineous weed cyperaceous weed”, of which, the occurrence of malignant weed species increased and caused more serious harm to rice.