This research investigated 147 samples collected from diarrhea pigs, healthy pigs and environment of a large-scale farm in Guangzhou. Escherichia coli strains were isolated and identified according to GB 4789.6-2016, and their susceptibility to 12 antibiotics and corresponding resistance genes were analyzed using the K-B disc diffusion method and polymerase chain reaction (PCR), respectively. Results revealed a total of 115 strains of E. coli. Drug resistance to sulfamethoxazole, levofloxacin, gatifloxacin and ciprofloxacin was high (over 30%), to gentamicin, ceftazidime and Aztreonam was moderate (20%~30%), and to polymyxin B, tigecycline and imipenem was relatively low (< 15%), with sensitivity to meropenem also detected. Multi-drug resistance (resistance to strains ≥ 3) was observed in 46.09% strains, with the strains from the diarrhea pigs being more resistant than those of the healthy pigs and environmental samples (p < 0.05, χ2-test). The isolated strains carried high levels of genes encoding resistance to drugs, among which the detection rates of ant(3'')-Ⅰa, aac(3')-Ⅰb, sul1, aac(3)-Ⅱb, blaTEM, blaCTX, tetM genes over 50%, thus suggesting the major resistance mechanism for the strains isolated in this study. The results of present study indicated the serious contamination with E.coli strains in this farm and their high antibiotic resistance. Relevant departments should provide supervision and guidance on the use of appropriate antibiotics for the effective prevention and treatment of diarrhea pigs.