The invention discloses a preparation method of a solid-phase micro-extraction coated optical fiber used for water quality detection. The preparation method includes the steps of: S1) uniformly mixing P123 and an ethanol solution, adding a silicon-based mesoporous material, and performing ultrasonic dissolution at 50-60 DEG C to prepare a mixed liquid; S2) performing surface treatment to a stainless steel wire, placing the stainless steel wire in a centrifugal tube filled with the mixed liquid, performing centrifugation, taking the stainless steel wire out, completely volatilizing ethanol at room temperature, and performing vacuum drying at 110-130 DEG C to prepare the solid-phase micro-extraction coated optical fiber. The invention also discloses the solid-phase micro-extraction coated optical fiber for water quality detection, which is suitable for detection of benzene-series compounds and heavy metals in water. The solid-phase micro-extraction coated material is prepared with P123 as a template agent, which is compounded with a silicon-based mesoporous material in situ, so that selectivity of the extraction optical fiber is improved and detection sensitivity is increased.