A new in-situ sampler and method for sampling porewater in mire profile and gases in upland soils are devised. The sampler includes four parts: a syringe, a three-way valve, a stainless steel capillary and a capillary end protector for preventing soil and/or plant residue to block the inlet. By using this sampler, porewater can be sampled from different layers of a profile not only without disturbing either the profile or the porewater therein, but also with the samples completely intact from air during the sampling process, thus ensuring the collected porewater real representative of the mire profile porewater consequently it can be used in a series of studies on such as mechanism for methane production, oxidation and emission.