To prepare a film having excellent temp. maintaining properties, incineration properties, mechanical properties, or the like, by employing a polymer contg. a specific structural unit in the main chain.

A polyvinyl alcohol and a thermoplastic resin having a boron- contg. group such as a boronic acid are blended and then extruded in the hot molten state to obtain a polyvinyl alcohol type polymer contg. 0.001-10 mol.%, pref. 0.005-3 mol.%, in the main chain, of a structural unit of the formula (wherein R1 is H or a 1-8,000C alkyl; and R2 is a 100-10,000C alkyl). Five to 60 wt.%, pref. 10-40 wt.% of this polyvinyl alcohol type polymer together with a polyolefin type resin, and optionally an additive such as an antioxidant, a plasticizer, a heat stabilizer, a UV absorbing agent, an antistatic agent, a lubricating agent, a colorant, a filler, a temp. maintaining agent and an anticlouding agent, are compounded and extruded into a film to produce an agricultural film. Thus, an agricultural film is obtd. with good transparency and giving off no poisnous gases during incineration.