YOF-HY submicron crystals prepared by hydrothermal synthesis and high temperature calcination have been demonstrated to possess Pure Upconversion (UC) luminescence and sensitive temperature feedback properties for laser display and real-time temperature monitoring in complex environments. In recent years, the fine optoelectronics industry, especially in the field of photonic devices and non-contact temperature sensing, has witnessed a growing requirement for optical temperature measurement materials in terms of clear presentations and accurate test records. Among many temperature sensing materials, rare earth doped upconversion luminescent fluorophor which can realize temperature sensing by using their own non-thermal coupled energy levels are ideal optical temperature measuring materials. Compared to traditional contact temperature measurement techniques, the non-contact temperature measurement based on Fluorescence Intensity Ratio (FIR) is a promising temperature sensing technique with favorable sensitivity, high accuracy, low environmental dependence, which avoids the spectral loss and excitation source fluctuation. UC fluorescent materials have attracted widespread interest owing to their excellent optical properties such as pure luminous, rapid response and real-time feedback demonstrated in various optoelectronic devices. Rare-earth ions are inherently low in luminescence efficiency, but the introduction of sensitizers will produce strong characteristic fluorescence by increasing the absorption of infrared photons and transferring energy to the rare-earth ions. Among the rare earth ions,Ho³⁺ has attracted great focus according to its special energy level structure which has been used to achieve strong visible UC luminescence with great temperature sensing potential, meanwhile the introduction of Yb³⁺ ions as a sensitizer can enhance the intensity of UC emission in Ho³⁺ ions-doped materials at the pumping of ~980 nm lasers. Among UC luminescence materials, fluorine oxides, with their lower phonon energies and stronger inversion asymmetry, contribute to improve the probability of radiation transition and obtain more efficient UC luminescence for higher sensitivity temperature monitoring. In this paper, the fabrication and temperature sensing luminous properties of the holmium-doped yttrium fluoride oxide submicron crystals are reported. The crystal structures are characterized by Scanning Electron Microscopy (SEM) and X-ray Diffractometer (XRD), confirming that the powder is YOF with the submicron structure. The UC luminescence performance of the crystal particles has characterized under 977 nm laser pumping. It is illustrated that both green and red light emissions from UC luminescence are two-photon excitationprocesses through power dependence. In the aspect of fluorescence quantum characterization, the spectral power distributions of the samples are presented with the fluorescence spectroscopy test system. Absolute quantum parameters such as the net photon distributions and quantum yields are calculated. When the excitation power density is increased to 73 mW/mm², the green and red UC emission spectral powers are 0.31 μW and 0.10 μW, respectively, demonstrating that the Ho³⁺/Yb³⁺ co-doped YOF submicron crystals are efficient luminous materials. The quantum yields (QYs) of green and red emissions from Ho³⁺ under 977 nm laser excitation are derived to be 2.97×10^-5 and 1.40×10^-5 respectively when the pump power density arrives at 73 mW/mm², and the high photon generation efficiency ensures sufficient fluorescence intensity for tracing temperature feedback. For temperature sensing, the thermal behavior of Ho³⁺ has been investigated using a FIR system with two non-thermal coupled energy levels. The absolute sensitivity (S_A) and relative sensitivity (S_R) of the YOF submicron crystals have been calculated. S_R is an indispensable parameter which is independent of material properties and enables direct quantitative comparison of temperature sensing properties in different samples. The maximum S_R is 0.437% K^-1 at 303 K, and maintains at 0.331% K^-1 when the temperature has increased to 433 K. Finally, temperature cycling tests have been conducted on the YOF submicron crystals, demonstrating that the submicron crystals have good reproducible properties and is an excellent candidate for temperature monitoring. Therefore Ho³⁺/Yb³⁺ co-doped YOF submicron crystals provide a potential option as an efficient luminescence and high temperature sensitivity material for the field of temperature sensing.