THIS STUDY WAS CONDUCTED AT IRANIAN PLANT PROTECTION RESEARCH FARM AT KARAJ, IN 2009 TO EVALUATE THE EFFECTS OF DIFFRENT PLANTING PATTERNS, TIMS OF MECHANICAL CONTROL AND HERBICIDES APPLICATION ON PERCENTAGE OF DENSITY AND BIOMASS REDUCTION OF WEEDS IN SUGARBEET FARMS.THE EXPERIMENTAL DESIGN WAS SPLIT-SPLIT PLOT BASED ON RANDOMIZED COMPLETE BLOCK DESIGN (RCBD) WITH FOUR REPLICATIONS. PLANTING PATTERN CONSIDERED AS MAIN-PLOT IN THREE LEVELS (INCLUDING: SINGLE ROW PLANTING 60*60 CM, TWIN ROW PLANTING 60*40 CM AND SINGLE ROW PLANTING 50*50 CM), TIME OF MECHANICAL CONTROL IN THREE LEVEL AS SUB-PLOT (INCLUDING: MECHANICAL WEED CONTROL AT 4-6 LEAVES STAGE OF SUGARBEET, 10-12 LEAVES STAGE AND 14-16 LEAVES STAGE), AND HERBICIDS AS SUB-SUB-PLOT IN TWO LEVELS (INCLUDING GOLTEX+BETANAL PROGRESS A.M AND SAFFARI+BETANAL PROGRESS A.M).RESULT SHOWED THAT TIMES OF MECHANICAL CONTROL AND HERBICIDES HAVE THE MOST REDUCTION ON DENSITY AND BIOMASS OF WEEDS (CHENOPODIUM ALBUM AND AMARANTHUS RETROFLEXUS).BEST RESULTS WERE ACHIVED IN MECHANICAL CONTROL AT 4-6 LEAVES STAGE AND THE BEST HERBICIDE WAS GOLTEX+BETANAL PROGRESS A.M. PLANTING PATTERN ALSO HAD SIGNIFICANT EFFECTS ON WEEDS BIOMASS BUT COULD NOT CONTROL THIER DENSITY.