A composition and a manufacturing method of a highly flame-retardant and low-smoke extruded polyvinyl chloride pipe are provided. The composition includes a polyvinyl chloride resin material, a flame retardant additive and a carbon forming additive. The polyvinyl chloride resin material is in an amount between 10 PHR (parts per hundred resin) and 90 PHR. The flame retardant additive is in an amount between 0.5 PHR and 2.0 PHR, and is a phosphorus-containing flame retardant modified by a modifier. The carbon forming additive is in an amount between 0.2 PHR and 1.0 PHR. The carbon forming additive is at least one material selected from a group consisting of zinc chloride, zinc stearate, calcium stearate, zinc hydroxystannate, anhydrous zinc stannate, zinc phosphate and zirconium phosphate. A total added amount of the flame retardant additive and the carbon forming additive in the composition is not greater than 3 PHR.