In order to avoid the solid invade damage of drilling fluid in Shunbei ultra-deep carbonate reservoir, anti-temperature and anti-calcium viscosifier SMVIS-1 for formate solid-free drilling fluid was synthesized by free radical polymerization with acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, dimethylaminoethyl methacrylate and a polycarboxylic monomer as raw materials, and an anti-temperature and anti-calcium solid-free drilling fluid was developed with SMVIS-1 as the core additive. The evaluation results show that SMVIS-1 can withstand temperatures up to 240 ℃ in potassium formate solution, and can resist 15 000 mg/L Ca²⁺ pollution after aging at 180 ℃. The drilling fluid system has a temperature resistance up to 220 ℃, calcium pollution resistance of up to 15 000 mg/L under 180 ℃, density range of 1.10~1.55 g/cm³, HTHP (high temperature high pressure)filtration loss less than 14 mL, and permeability recovery value of 95.6%~98.3%, demonstrating good rheological and fluid loss control properties and other performance such as reservoir protection. The drilling fluid has been applied in more than 20 wells in Shunbei and Tahe oilfields in Xinjiang. During the drilling process of Shunbei 5-4HCH, the rheology and filtration loss of drilling fluid remained stable, the rock deberis returning was good, the friction force was less than 10 t, the pressure drag phenomenon did not occur, and the tripping was smooth. Compared with adjacent wells, the daily oil production has increased by 13.7% to 34.3%, proving a good reservoir protection effect of anti-temperature and anti-calcium solid-free drilling fluid.