A fluorescent lamp uses new cold-end technology or an enveloped fluorescent lamp with high surface load. The lamp features a lamp tube, cathode, stem cap and wire, such that one end of the wire connected to the cathode is fixed on the stem cap and the other end of the wire is led out from the lamp tube. At least one cavity tube connecting through the lamp tube is disposed on the side of at least one lamp tube. Advantages of the fluorescent lamp include: (1) the temperature of cavity tube is not influenced directly with electrical arc since there is no discharge through appended cavity tube, thus mercury-vapor pressure adjustment with cold-end is made possible; furthermore, mercury-vapor pressure is decreased significantly on energy saving lamps with high power or lamps in high environmental temperature; (2) by adjusting the length and/or position of the cavity tube, mercury-vapor pressure in the lamp tube can be adjusted efficiently; (3) if amalgam is required for the lamp tube, the adjustment work becomes easy and efficient by positioning the amalgam at the coldest point; with adding auxiliary cathode selectively, good luminous flux is formed rapidly when the lamp is turned on initially; (4) the effective service life of the lamp tube is lengthened since the harmful materials to luminous flux output produced during lamp operation are collected at the cold-end of cavity tube.