An image pick-up optical lens assembly, sequentially arranged from an object side to an image side along an optical axis, comprises: a first lens element with a positive refractive power having a convex object-side surface, a second lens element with a negative refractive power, a third lens element with a positive refractive power, a meniscus fourth lens element with a positive refractive power having at least one aspherical optical surface, and a fifth lens element with a positive refractive power having at least one inflection point on the optical image-side surface. Additionally, the image pick-up optical lens assembly satisfies several particular conditions. The invention possesses features such as good aberration compensation, well-performed modulation transfer function and short total length of lens assembly applicable for compact cameras and mobile phones.