The invention discloses a preparation method capable of regulating and controlling the molecular weight of poly(dimethylsiloxane-co-methylvinylsiloxane) and the distribution thereof. The preparation method comprise the following steps: mixing dimethylcyclosiloxane and an alkali catalyst, and inflating nitrogen for 0.5-1.5 h; raising the temperature to 90-130 DEG C, and performing a polymerizationreaction for 2-6 hours to obtain a reaction solution; adding methylvinylcyclosiloxane and an end-capping agent into the reaction solution, and continuing the polymerization reaction for 2-6 hours to obtain a crude product; and posttreating the crude product, precipitating methanol stepwise, centrifuging, and finally performing rotary evaporation to obtain the poly(dimethylsiloxane-co-methylvinylsiloxane). By the preparation method, the preparation process is simple, the posttreatment is convenient, the product yield is high, and the molecular weight and the distribution thereof are relativelyeasily controlled; the preparation method can be widely applied to reinforcement and modification of silicone rubber and silicone resin, can be applied to modification of magnetic nanoparticles and medicine release, and can be applied to improvement on the performance of a release agent, a demoulding agent, a personal skin-care product and the like.