Objectives The changes in the content of heavy metal in pig manure and the concentration of ammonia in pig house at different stages of growth were analyzed to provide basic data for evaluating the safety of returning livestock and poultry manure to the field and improving the breeding environment of pig herds. Methods Three pig herds including breeding sows, conservation pigs, and fattening pigs were selected from four large-scale farms in Yi County, Jinzhou City, Liaoning Province. One mixed sample of 6 pig manure was collected from each herd. A total of 20 samples were collected, with a total of 120 pig manure. The content of heavy metal in pig manure was detected using an inductively coupled plasma generator (ICP) after ashing and digesting the samples. The concentration of ammonia in different pig houses was numerically monitored with a portable ammonia detector. Results The highest content of zinc, copper, and arsenic in pig manure from fattening pigs was 567.6 mg/kg, 104.3 mg/kg, and 38.9 mg/kg, respectively, exceeded the limit of heavy metal specified in GB/T 25246-2010 for fertilizing vegetables in soil (pH<6.5). The content of heavy metal in pig manure from breeding sows and conservation pigs reached the standard. The values of ammonia detected in the pig house of three pig herds were all less than 20 mg/m³. Conclusions There was a phenomenon of heavy metal exceeding the standard when the manure from fattening pigs in four farms was directly returned to the field for vegetable cultivation. Therefore, the manure from fattening pigs cannot be reused as fertilizer or feed. The values of ammonia detected in four breeding farms are all within the normal range and will not cause harm to farming technicians and pigs.