Background: Cholinesterase is an enzyme that has a role to moveglands, muscles and nerves harmoniously and organized. This enzyme is a form of biological catalysts that is located within the body tissue. If the Cholinesterase activity of body tissue is decreased, it will cause body poisoning. Cholinesterase levels in the body are affected by pesticide exposure. The longer working period needed, the spraying is more often done. The longer working period the more pesticides are absorbed in the body. Aims : Analyze the relationship between the time of working period with cholinesterase blood levels among pesticides sprayer workers in palm oil plantation. Methods: This research is an analytic observational study with cross sectional approach which analyzed by chi square test. Primary data obtained from the laboratory tests with spektofotometer on cholinesterase blood levels. This data is also resulted from interview used a questionnaire towards pesticides-spraying workers in the oil palm plantations PT. Agro Bukit KotawaringinTimur. Results: The chi square test among 102 samples showed that the p-value = 0.241 (> 0.05), means that there is no relationship between working period and cholinesterase blood levels. Conclusion: There is no relationship between working period and cholinesterase blood levels among pesticides-spraying workers in the oil palm plantation.